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NBSIR 75-940

The National Measurement

System for Spectrophotometry

William H. Venable, Jr.

Institute for Basic Standards

National Bureau of Standards

Washington, D.C 20234

November 1977

Final

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». DEPARTMENT OF COMMERCE

nONAL BUREAU OF STANDARDS
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NBSIR 75-940

THE NATIONAL MEASUREMENT

SYSTEM FOR SPECTROPHOTOMETRY

William H. Venable, Jr.

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

'November 1977

Final

U.S. DEPARTMENT OF COMMERCE, Juanlta M. Kreps, Secretary

Dr. Sidney Herman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

FORWORD

This is one of the reports from the 1972-75 NBS Study of the National Measurement

System. It deals specifically with the current structure, status, and trends of the

system used in this country for the measurement of transmittance, reflectance and

related quantities.

The "Concept of a National Measurement System" has been discussed by NBS authors

and spokesmen for a number of years, since the publication by Dr. R. D. Huntoon of

an article by that title in the October 6, 1967 issue of Science (Vol. 158, No. 3797, pages 67-71). Dr. Huntoon began his article with the following paragraph:

"Concurrently with the growth and industrialization of this nation, there has

. developed within it a vast, complex system of measurement which has made

possible the very growth that brought the system into being. This National

Measurement System (NMS) stands today as one of the key elements in a worldwide measurement system that links all major nations together in a consistent,

• compatible network for communication and trade."

The U. S. National Measurement System is defined as comprising all of the activities

and mechanisms--intel lectual and operational, technical and insti tutional --used

by this country to produce the physical measurement data needed to create the objective, quantifiable knowledge required by our society. This knowledge is used to describe, predict, communicate, control, and react, in many aspects of our personal

and social lives, science, and technology.

Dr. Huntoon continued his discussion in 1967:

"Our National Measurement System is one of a number of mutually interacting systems

within our technologically based society that form the environment in which the

individual citizen must live and function. Familiar examples are the communication, transportation, educational, medical and legal systems, all of which may

be included under the general heading of social systems."

"In view of the demonstrated value of the systems approach for the understanding and

improvement of hardware such as computers and weapons, some of these social systems

are being subjected to the same type of analysis. The National Measurement System,

which evolved in this country with little formal recognition as a system, is now

being examined in this way at the National Bureau of Standards (NBS) which undertook the study of the National Measurement System partly because of the all -pervasive nature and great economic importance of the nation's measurement activities,

and partly because of the challenge to NBS in putting its splendid new facilities

to optimum use for the benefit of the nation. Such optimum use can be approached

only when the National Measurement System, of which NBS is a central element, and

the services it requires for effective operation are sufficiently well understood."

Over the years both before and since 1967, NBS has taken a number of approaches to the study of our national system for physical measurements. The current series of

studies was initiated in 1972 by Dr. Ernest Ambler, then Dr. Huntoon's successor as Director of the NBS Institute for Basic Standards, now Director of the Bureau.

, The reports of these studies are being presented to the public at large for the purpose of increasing national understanding, and the operational effectiveness, of our

National Measurement System. They are presented as an intial or interim, not final,

word on the subject. NBS welcomes contributions from all sectors of the System

• which can aid it in increasing its understanding of and effectiveness in supporting

that System.

iii
NOTICE

A diligent effort has been made to make this

report comprehensive and accurate as of Marcti

1975. Since that time no important changes or

additions have been made. There have, however,

been a few significant changes in the National

Measurement System for Spectrophotometry. The

interested reader may wish to contact the author

for his opinions on these changes.

i V
CONTENTS

Page

FORWORD iii

NOTICE iv

EXECUTIVE SUrMRY 1

1. INTRODUCTION 2

2. STRUCTURE OF THE MEASUREMENT SYSTEM 2

2.1 Conceptual System 2 2.2 Basic Technical Infrastructure 3

2.2.1 Documentary Specification System 3

2.2.2 Instrumentation System 4

2.2.3 Reference Data 5 2.2.4 Reference Materials 5 2.2.5 Science and People 5

2.3 Realized Measurement Capabilities 6

2.4 Dissemination and Enforcement Netvyork 7

2.4.1 Central Standards Authorities 7 2.4.2 State and Local Offices of Weights and Measures 7 2.4.3 Standards and Testing Laboratories and Services 7 2.4.4 Regulatory Agencies 7

2.5 Di re ct Measurements 7

2.5.1 Analysis of Suppliers and Users 7 2.5.2 Highlights re Major Users 12

3. IMPACT, STATUS AND TRENDS OF MEASUREMENT SYSTEM 12

3.1 Impact of Measurements 13

3.1.1 Functional, Technological, and Scientific Applications . 13

3.1.2 Economic Impacts - Costs and Benefits 14

301.3 Social, Human, Person-on-the-Street Impacts 14

3.2 Status and Trends of the System 15

4. SURVEY OF NBS SERVICES 15

4.1 The Past 15

4.2 The Present - Scope of NBS Services 16

4.2.1 Description of NBS Services 16

4.2.2 Users of NBS Services 17

4.2.3 Alternate Sources 17

4.2.4 Funding Sources for NBS Services 17

4.2.5 Mechanism for Supplying Services 18

4.3 Impact of NBS Services 18

4.3.1 Economic Impact of Major User Classes 18

4.3.2 Technological Impact of NBS Services 18

4.3.3 Payoff from Changes in NBS Services 18

V
I

I Page

4.4 Evaluation of NBS Program 18

4.5 The Future 19

5. SUMMARY AND CONCLUSIONS 19

APPENDIX A. METHODOLOGY OF THE STUDY 20

APPENDIX B. A PROPOSED DIRECTION FOR NBS EFFORTS 21-28

APPENDIX C. EVALUATING THE BENEFITS OF IMPROVING SPECTROPHOTOMETRIC

MEASUREMENTS 29-41

APPENDIX D. FACTORS AFFECTING ACCURACY IN SPECTROPHOTOMETRIC MEASUREMENTS . 42-53

APPENDIX E. WHAT IS AN APPEARANCE MEASUREMENT? 54-65

APPENDIX F. REFERENCES 66-93

LIST OF TABLES

Table 1. Direct Transaction Matrix for Spectrophotometry 9

vi
ABSTRACT

A special study of the spectrophotometri c measurement system

was made in order to determine what could be done to improve these

measurements and what benefits would result from the improvements.

It was found that improvements in the measurements could make large

contributions to productivity, health, and safety in the U.S., and

that, because of the fragmented nature of this measurement community,

the improvements in spectrophotometri c measurements can be realized

most efficiently through the efforts of a centralized agency such

as NBS. With the aid of this study, the program in spectrophotometry

at NBS has been revised in order to bring about these improvements

more rapidly and effectively.

Key words: Absorption spectra; automation, chemical analysis;

colorimetry; heat transfer; reflectance; remote sensing; retroreflectance; spectrophotometry; transmi ttance.

vii
1;
THE NATIONAL MEASUREMENT SYSTEM FOR SPECTROPHOTOMETRY

Wil 1 iam H. Venable, Jr.

Optical Physics Division

August, 1977

EXECUTIVE SUMMARY

This microstudy covers the field of spectrophotometry and particularly the work in this field being conducted in the Radiometric

Physics Section at NBS. In general, spectrophotometry provides an answer to such questions as how much light is reflected by an object or transmitted through it. ("Light" is used here in a very general sense which includes the light we see and other electromagnetic radiation in the adjacent portions of

the spectrum which behaves in a manner simiar

to light.) The technological significance of

spectrophotometric measurements lies in its use as a tool for determining something about

the object. Combined with a knowledge of the

way the human eye functions, spectrophotometry

can be used to predict and control the way an object will appear. Thus spectrophotometry

can become the "eyes" for the automated production and quality control in the manufacture of objects and materials in which ap- pearance is important. Taken with knowledge

of the optical properties of chemicals, spectrophotometric data forms a basis for quantitative chemical analysis in a huge variety of

fields from clinical testing to manufacturing.

There are countless other applications in such areas as photography, remote sensing, warning

devices for safety, and non-destructive inspection of agricultural products.

As the foregoing indicates, the user com- munity is huge. The processes in which spectrophotometric measurements are or could be

significant are estimated to account for about

one-fourth of the gross national product. It should be pointed out, that in most cases, the

spectrophotometric measurement is only a small

part of the total operation for a given user.

As a result, the spectrophotometric measurement community for the most part is made up of

a huge number of widely diverse individuals

who use spectrophotometry as a tool and who

do not have a strong knowledge of the field.

They rely on the instructions which come with

their instruments and on standard test procedures. This large, highly diverse community

is the productive level of the spectrophotometric community.

At the next level above the user community

lies practically all of the rest of this

measurement system, e.g., the instrument man- ufacturers, the military, government, and

commercial measurement laboratories, and the

many committees which develop and publish the

standard measurement techniques interact

directly or nearly directly with the user

community. The standards and services

supplied by this second level are adequate

for some applications but if the full value

of spectrophotometry is to be realized, the error in these measurements must be reduced

by a factor of ten.

In order to bring about such an improvement in the measurement system, a strong

capability for highly accurate measurement

must be built up. The instrumentation and

labor required for this effort would be too much for any one of the instrument manu- facturers or commercial laboratories to handle, much less for any individual user. Economically, this capability should be in

a central laboratory, and, in the interest

of fairness, this laboratory, should be on "neutral ground". Quite obviously, NBS is the laboratory for such universal standardization of these measurements to take place.

From the mid 1950's until very recently, the

spectrophotometry program at NBS was small

and geared principally to measurements as a service to the rest of NBS and to other

government agencies. However, during the

past five years, the spectrophotometry program

at NBS has been revised and our measurement

capability is being built up to the point

where we can supply the leadership required

for increasing the accuracy and extending

the range of spectrophotometric measurements.

Through this study and through our routine

contacts with the technical community, we have clearly recognized the magnitude of the user community and the potential advantages

which can come from an order of magnitude

improvement in the measurements. We have

gained an insight into what needs to be done

by NBS in this respect and have initiated a program through which we can do our part.

The new NBS capability should be fully

developed during the next five years, at which time the full impact of our efforts

will begin to be felt. The potential benefits

which can be obtained from improving spectrophotometric measurements is estimated to be

as great as two billion dollars annually. It

is our intent to provide leadership which

will enable the scientific, technical and

industrial community to obtain those benefits

as readily as possible.
THE NATIONAL MEASUREMENT SYSTEM FOR SPECTROPHOTOMETRY

1. INTRODUCTION

What kind of measurement system is named

by a word like "spectrophotometry" which has

nearly as many interpretations as there are people who use it? What kind of a measurement system is one which really exists at only two levels? And what is NBS doing in

the midst of all this? The purpose of this

brief report is to clarify a few things about

this important field of measurement.

Spectrophotometry, as used here, is a term which includes all measurements which

quantify in terms of radiant power the way

light and similar electromagnetic radiation

is altered by interacting with objects. These

measurements answer such questions as, "What

fraction of the incoming light is reflected

from an object?" and, "What fraction of the

incoming light passes through an object?"

The importance of these measurements lies

in the vast extent of their applications.

Because of their wide use, a small improvement in the measurements and an accompanying

small percentage of saving to each user can make a very large contribution to the economy.

During the five to ten years preceding the

initial study in 1972, NBS did not assert

strong leadership in this part of the measurement system. Because of the fragmented nature

of the user community, advancement has been

spotty, and the advances made by one group

of users have not been passed along to the

others. During the past four years, the

Institute for Basic Standards (IBS) and the

Institute for Materials Research (IMR) in NBS

have been building up programs in spectrophotometry directed toward providing the

leadership which is needed. These circumstances render inappropriate the negative

approach suggested by the question, "What

would happen if NBS were not involved in

spectrophotometry?", and instead call for a positive approach through answering the

question, "What can be gained by strong NBS

involvement in spectrophotometry?" It is to the answer of this question that this study

and the reports growing out of it are directed.

The study on which this report is based

was begun before the National Measurement

System (NMS) study which was the basis of

most reports in this series. In January

of 1971, the Spectrophotometry Section was made a part of the newly formed Optical

Radiation Section in a reorganization within

the Institute for Basic Standards (IBS). At

that time, the Institute Director called for

a thorough investigation of the needs in the

field and the activities of the Spectrophotometry Section in the past to determine what course of action NBS should follow concerning

2

this part of the measurement system. This

investigation was completed and the results

were presented to the IBS director in

December of 1972 in a report entitled The

Role of IBS in Spectrophotometry . The findings

in that report, along with other information

acquired from other sources, particularly

from NBS staff members in the IMR spectrophotometry group, are summarized here in a form consistent with that used for the other

summary reports on the National Measurement

System. Certain sections of the 1972 IBS

report are included in their entirety as appendices to the present report as background

information.

The spectrophotometry study led to a very

definite conclusion. With a fairly substantial improvement in its instrumentation and

by using a different over-all approach from

the one it used in the past, NBS could make

a very large contribution to the scientific

and technical community in spectrophotometry,

and this could be done with no increase in

the number of NBS staff members working in

the area.

2. STRUCTURE OF THE MEASUREMENT SYSTEM

2.1 Conceptual System

The quantity being measured in spectrophotometry is the ratio of a given portion

of the radiative power transmitted by or reflected from an object to the radiative

power incident on the object. The particular

units involved in these ratios depend upon

the particular type of spectrophotometric

measurement. In some cases it is necessary

to involve units of area, for which the

square meter is the basic SI unit, and in

other cases solid angle in steradians is

involved. Generally, however the stated

measured values are made dimensionless by

comparing the way in which the object being

measured interacts with radiation to the way

in which some standard object, either real or idealized, would interact under the same

ci rcumstances

The primary standard for spectrophotometric

measurements is simply an accurately made

measurement. In principal anyone can make

accurate primary measurements, but in fact

few laboratories have the facilities to make

all of the peripheral measurements required

to be assured of accuracy. However, a mea- surement in which the optical properties of

two objects are compared can be made with

high accuracy relatively easily. Therefore,

an individual user tends to obtain a transfer standard, an object which is similar to the one he wishes to measure and one which
has stable properties which have been accu- rately measured. He then compares the object

he is trying to measure to the transfer

standard.

In most spectrophotometric measurements,

there is a definite limit to the need for

accuracy. The limit in quality control applications, for example, can grow out of an economic compromise or be determined by the

magnitude of random variations in the production process. In clinical chemistry, for

example, sample preparation problems usually

place an upper limit on the accuracy of the

results of the test. Similar considerations

apply to the many other applications. In each application, the spectrophotometric

measurement need only be accurate enough so that its uncertainty is three to ten times

smaller than the range of variation allowed

for that application. From this viewpoint,

the uncertainty in the measurement process

itself is currently three to ten times too

great in a very large percentage of the

appl i cations.

2.2 Basic Technical Infrastructure

If one thinks of the basic technical infrastructure as having two dimensions, depth in

terms of the number of levels in the measurement chain and width in terms of the number

of different groups involved at any particular

level, then one can certainly say that the

basic technical infrastructure for spectrophotometry is not very deep but it is quite

wide. It is almost one-dimensional. As the

system currently operates, there are usually

just two levels of standardization, but there

are many separate groups of users with

activities which are almost in parallel. The

reason for this will become more apparent

with the discussion of the details of the

infrastructure in the following paragraph.

2.2.1 Documentary Specification System

2.2.1.1 Standardization Institutions

There is no standardization organization

devoted specifically to spectrophotometric

measurements, but there are literally dozens

of organizations which write spectrophotometric specifications and documents giving

standard measurement procedures. Each organization within a given industry or field tends

to adapt one of the more general documentary

standards to its own special purposes with

mixed degrees of success. The general documentary standards are written internationally

by such organizations as Commission Internationale de I'Eclairage (CIE) and the International Organization for Standardization

(ISO). Within the United States there are

two principal organizations which produce

general documentary standards, the American

National Standards Institute (ANSI) and the

American Society for Testing and Materials

(ASTM). Beyond these, there are trade

associations through which groups of users adapt these measurements to their own purposes. The following list, although by no means complete, illustrates the range of

technology encompassed by these associations

representing users of spectrophotometry:

0 American Association of Clinical Chemists

0 American Association of Textile Chemists

and Colorists

0 American Ceramic Society, Inc.

0 American Chemical Society

0 American College of Prosthodontists

0 American Dental Association

0 American Institute of Architects

0 American Oil Chemists' Society

0 American Society for Photogrammetry

0 College of Clinical Pathologists

0 Color Marketing Group

0 Dry Color Manufacturers' Association

0 Federation of Societies for Paint

Technology

0 Graphic Art's Technical Association

0 Illuminating Engineering Society

0 Institute of Food Technologists

0 National Association of Printing Ink

Manufacturers, Inc.

0 National Paint, Varnish, and Lacquer

Association

0 Optical Society of America

0 Paperboard Packaging Council

0 Pharmaceutical Manufacturers Association

0 Research and Engineering Council of the

Graphic Arts Industry, Inc.

0 Society of Motion Picture and Television

Engineers

0 Society of Plastics Engineers, Inc.

0 Technical Association of the Graphis Arts

0 Technical Association of the Pulp and

Paper Industry

Through the recent years, the governmental

legal and regulatory use of these measurements

has been gradually increasing. Some of the

regulatory agencies which have been or are becoming involved are the Department of

Transportation and the Consumer Product

Safety Commission in connection with reflectors and fluorescent warning markers for

safety, the Food and Drug Administration in

connection with testing foods for additives,

and the Environmental Protection Agency in

connection with remote sensing of pollution.

The General Services Administration also

places certain requirements on the optical

performance of paints and reflectors purchased

by the United States Government. The military

agencies have tended to establish their own

3
primary measurement capabilities in such

laboratories as the Arnold Development Center,

Michael son Laboratory, Naval Electronics

Laboratory, and Newark Air Force Station.

2.2.1.2 Survey of Documentary Standards

The organizations mentioned in the

preceding paragraphs write the documentary

standards which govern the measurement procedures used in spectrophotometry and which

specify the optical properties of materials.

Internationally, the International Organization for Standardization writes specific

test methods which are then adopted by

industries and governments in various

countries. The Commission Internationale

de I'Eclairage operates in a slightly different mode in which it recomniends definitions

and procedures to be used in the measurements.

These recommendations are then adapted by

various local, national, and international

standardization organizations as they write

specific documentary standards of their own.

In the United States, the largest writer

of documentary standards involving spectrophotometric measurements is the American

Society for Testing and Materials. There

are several documents covering spectrophotometric measurements in a very general way

and approximately fifty testing methods which

incorporate spectrophotometric measurements

as part of a more general testing procedure.

In addition, professional and trade associations incorporate spectrophotometric measurements into their test procedures. As a typical example of this, consider the

Universal Product Code Symbol Specification

Code put out by the Uniform Grocery Product

Code Council. This document specifies the

bar code symbols to be used in identifying

grocery products for automated checkout and

inventory. This document specifies in

detail the shape and structure of the symbols

to be used, how they can be scaled larger or smaller, how they are to be evaluated for

distinctness of printing, etc. A five page

section of this forty-three page document

deals with the contrast, opacity, colors,

and other spectrophotometric properties of

the printing and specifies the instruments

to be used in testing for these properties.

If one imagines hundreds of similar documents

put out by dozens of independent groups,

government agencies, and the military, he

has an idea of the nature of the documentary

standards for spectrophotometry. The significance of these standards comes from the

large number of them and the wide range of

activities which they affect.

2.2.2 Instrumentation System

2.2.2.1 Measurement Tools and Techniques

A typical spectrophotometric instrument

consists of three parts, a source of radiation, a sample holder, and a radiation

receiver. The source produces a given spectral and geometrical distribution of radiation upon the sample region, the sample

holder places the sample in a given orientation within the radiation, and the receiver

delimits the part of the radiation to be

observed and detects it. Most modern instruments also include electronic circuitry to control the source and "read" the detector

signal although some instruments are still

produced which rely upon the human eye as a detector. The design of a large portion of

the instruments developed for regular commercial sale are governed by the general specifications of the ASTM or related measurement

methods with regard to the angles at which

the radiation is incident, its spectral

distribution, and the angles and wavelengths

at which the receiver is sensitive. There

is also a significant number of instruments

developed for special purpose measurements,

such as instruments which evaluate the

protein content of grains.

The instruments can be separated into two

general categories. In the first category

are those instruments for which the geometrical arrangement and strength of the outgoing

radiation is about the same as for the

incoming radiation. Such an instrument can measure its own incident radiation and hence

can establish a ratio without relying on a separate transfer standard for calibration.

In the second category are those instruments

in which the outgoing radiation differs

greatly in strength or geometrical arrangement from the incident radiation. In such

an instrument it is usually far more practical to calibrate the instrument by

measuring a sample with known properties,

i.e., by measuring a transfer standard.

Since certain ranges of variations in the

measurement parameters are usually allowed

within a given class of measurements, it is

important that the calibrating laboratory

provide the value of a transfer standard

obtained with the particular instrument

with which the standard is to be used.

Since most measurements are designed to be

as insensitive as possible to peripheral

parameters, differences between instruments

can generally be taken into account through

rather simple correction formulae. In addition to calibration standards for the second

4
type of instrument, it is valuable in the case of both types of instruments to have

special transfer standards which can be used

to test for the quality of instrument performance, as, for example, to determine if

incident radiation is present at wavelengths

other than the desired one. Typically, a user will use carefully

preserved transfer standards to calibrate

and check out his instrument when it is initially put into operation and at rather

infrequent intervals to check it. After the

instrument is working properly, the user will

typically measure a separate "working standard", in those cases in which a transfer

standard is required for calibration, and

will use this for calibrations in his daily

operations. The transfer standards measured

by a primary calibration laboratory are not

used often, and they are deliberately chosen

to be very permanent. Furthermore, the

material usually has a rather low intrinsic

value, so that its main cost lies in the

labor required to measure it. In spectrophotometry, then, one has a measurement sys- tem in which standards are very important

but are cheap and long-lasting. As a result,

the size and importance of the measurement

system cannot be readily judged by either the

monetary value or the number of standards

which are issued.

2.2.2.2 The Instrumentation Industry

A spectrophotometric instrument is relatively expensive, ranging in cost from several hundred to tens of thousands of dollars

in cost. The instruments are quite longlived, however, so that the $100 million

annual expenditure on analytical spectrophotometers and the similar amounts spent on spectrophotometric instruments for other

purposes represents replacement and expansion

for a very large number of instruments in the

field. Because of the complexity of the

instruments, the user deals directly with the

instrument manufacturer or with his sales

representative. U.S. instrument companies

export about 10% of their products. Of the

instruments purchased in the U.S., about 40%

come from abroad, and a trend in the recent

past has been for a decrease in exports and

an increase in imports. The instrument manu- facturer typically supplies or recommends the

transfer standards to be used in calibrating

his product. Because of the de-emphasis of

spectrophotometry at NBS in the late nineteensixties, the standards issued by the manufacturers have not been properly traceable

to NBS standards or correlated with each

other.

2.2.3 Reference Data

The reference data which are generated

through spectrophotometric measurements are application oriented. These data are published in the literature connected with the

particular applications, as, for example,

published lists of absorption coefficients

of various chemicals in solution. The data

are not essential to making the spectrophotometric measurement, but rather they are

used in interpreting the results of the

measurement in connection with the particular

application. It is important, of course,

to have reference data on the materials and

components used in building spectrophotometers,

but this is of interest mostly to the relatively small community of instrument manufacturers which already have collected this

data.

2.2.4 Reference Materials

Spectrophotometric measurements measure

the properties of objects rather than materials. For example, the "reflectance of a powder" cannot be measured, although one can measure the reflectance of a pellet made by

pressing a layer of the powder onto a backing

material. Similarly the absorption of radiation by a particular chemical species is not measured directly, but instead one measures

the transmittance of a container filled with

a solution of the chemical and deduces the

absorption. Therefore, it only makes sense

to provide reference materials in the cases

in which the connection between the material

and the object made from it is particularly

simple. One such case is that of the stan- dard reference solutions produced for the

NBS Office of Standard Reference Materials

by the Institute for Materials Research

which is covered in a separate summary report.

For convenience in marketing, several types

of transfer standards such as filters and

reflectors are sold through the Office of

Standard Reference Materials, but these are

in reality standard reference objects, not standard reference materials.

2.2.5 Science and People

Many areas of technology provide support

for the spectrophotometric measurement system. In terms of the sources of radiation,

the older conventional radiation sources are constantly being improved, and new sources

such as lasers and light emitting diodes are being rapidly developed. As an outgrowth of

the interest in lasers and optical transmission lines, many new materials, optical

5
components and optical techniques have become

available, and similar advances have been

made in detectors. Dealing with the vast amounts of data generated in a set of spectrophotometric measurements has been a problem

in the past, but automatic data taking sys- tems and today's highly developed computers

have overcome this handicap. In short, the

technological advances of the past five to ten years have removed most of the obstacles

which have been in the way of improving

spectrophotometry in the past.

Since a large part of the technology and

science undergirding spectrophotometry is optical and thus depends upon knowing the

properties of optical materials, improved

spectrophotometry can be an aid in developing

optical technology. However, the greatest

flow of benefit will probably be from optical

technology through spectrophotometry to the

rest of the scientific community rather than

from spectrophotometry feeding back into

optical technology.

In the description of the infrastructure

in paragraph 2.2, the horizontal nature of

the community of users was emphasized. The

users in each given field usually have little

communication with one another. The professional societies of these groups, who write

the specialized test methods mentioned, tend

to publish their findings in the journals

connected with their own specialty. In some more complex fields there are specialized

courses offered in educational institutions,

as, for example, the course of color science

offered at Renssalaer Polytechnic Institute.

Some of the larger instrument manufacturers

conduct seminar courses in various industrial

centers. In the most part, however, the user

of spectrophotometry picks up his techniques

from the instruction manual with his instrument, from the textbooks and other literature

in his field, from his associates, and from

experience.

The educational background of the users

of spectrophotometry ranges almost continuously from the high school level for the

operator of a quality control test instrument on-line to the post-doctorate level for

the research chemist or meteorologist. There

are very few professional spectrophotometri sts outside of the instrument development and

standardization fields. To the typical user, spectrophotometry is a tool in his work, one

of many tools, and as a tool the spectrophotometer should be as simple and foolproof as possible. The less educated users cannot

understand the radiometric background behind

their measurements, and the more advanced

users should not have to constantly pay

attention to details of the measurement. The

principal need of a member of the user com- munity is to be supplied with the instruments,

methods and standards with which to carry

out his work effectively with as little difficulty as possible.

2.3 Realized Measurement Capabilities

As a general rule, the need for accuracy

in a spectrophotometric measurement is limited by very practical considerations

connected with the application. In appearance measurements, for example, the ability

of the human eye to distinguish differences

in appearance under the conditions peculiar

to a given application provides a limit beyond

which it is not necessary to push the measurement accuracy. If a spectrophotometric

instrument were used to control a finishing

process via a feedback loop, the instrument

should be a factor of three or so more discriminating than the eye in order to allow

the feedback system room to operate, but still

there would be a definite limit to the accuracy required. In chemical analysis, the

practical considerations of sample purity and

preparation limit the measurements, and in

quality control in general there is always

a point beyond which economic and other

practical considerations indicate the mea- surements should not be pushed. As a rule

of thumb, if the error in the measurement

is a factor of three smal ler than the uncer- tainty which can be tolerated in an application, the requirements for the measurement

have been satisfied.

In discussing the present status of the

measurements, one must distinguish carefully

between precision and accuracy. Precision,

can be defined as the ability of an instrument to repeat its own measurements from

minute to minute or day to day. High precision indicates that the instrument is stable, is insensitive to extraneous parameters such as temperature or humidity, and

has a low noise. As a result of technological

advances most modern instruments are more

than sufficiently precise to meet the requirements of the various applications. If an application requires measurements on only one

kind of object by only one instrument, and

if that instrument never changes, precision

is all that is required. However, in most

cases there is a definite need for accuracy,

i.e., the ability to measure a defined quantity. In general, the uncertainty in the

accuracy of spectrophotometric measurements

at present is generally a factor of three or

so larger than the uncertainty tolerable in the applications, in spite of the increased

precision of the measurements.

6
2.4 Dissemination and Enforcement Network

2.4.1 Central Standards Authorities

In international trade, there is a movement within the International Organization

for Standardization (ISO) to designate certain

laboratories as acceptable for providing

standards for a given type of measurement.

Those participating in the ISO program would

then agree to use transfer standards provided

by these laboratories. Within given countries, the national standardizing laboratories

generally offer calibration services for

spectrophotometri c measurements. The National

Bureau of Standards in the United States, the

Physi kal i sch-Techni sche Bundesanstaldt in

Germany, and the National Research Council

Laboratories in Canada, and the National

Physical Laboratory in England are four

laboratories which have strong programs in this area of measurement. With the exception

of those few cases in which specific governmental regulation requires the use of the

national laboratory, the effectiveness of the

national laboratory in providing standardization and measurement assurance is based

largely upon the respect which the technical

community has for the capabilities of the

national laboratory.

2.4.2 State and Local Offices of Weights and

Measures

State and local offices of weights and measures are almost totally uninvolved with

spectrophotometric measurements. However,

the procurement agencies for a number of

states and large localities maintain spectrophotometric measurement capabilities in their

laboratories in order to ascertain that specifications for items being procured are met

and as an aid to decisions in procurement by

competitive bidding.

2.4.3 Standards and Testing Laboratories and

Services

There are a few prominent large testing

laboratories which offer a fairly broad

range of spectrophotometric measurements

along with a variety of other measurement

services. In addition, many industries

which have spectrophotometric measurement

capabilities will perform measurements

for a fee providing the facilities are

not in use for company business and the

service does not offer advantage to a competing company.

2.4.4 Regulatory Agencies

Currently, the principal regulatory involvement with spectrophotometry has been in the

field of safety in which performance requirements for retroreflecti ve and fluorescent

warning devices are being spelled out. The

Consumer Product Safety Commission and the

States of California and New York have all

established regulations concerning reflectors

used on bicycles. The Department of Transportation has specified the performance of

the orange slow vehicle and emergency warning

triangles, and has begun a new investigation

into haze measurements on windshields.

2.5 Direct Measurements Transactions Matrix

2.5.1 Analysis of Suppliers and Users

The input-output matrix presented in table

?, with the corresponding key to the numbers

presented in table Lis an attempt to show

in compact form the extent and value of interactions between various groups in the spectrophotometric measurement community, to give

some idea of the way the role of these interactions is changing, and to indicate the

adequacy of such interactions as it is affected

by the quality and availability of spectrophotometric measurements. Although the large

variety of uses to which spectrophotometric

measurements are put prohibits a complete

listing of all of the suppliers and users, a few examples will be listed for each category

in order to clarify what is meant by that

category.

1. The Knowledge Community

This community consists of universities

and centers for pure research, the academic

and scientific organizations associated with

them, and the corresponding technical publishers. This section of the measurement

community both supplies and uses spectrophotometric measurement techniques and data

generated from spectrophotometric measurements .

2. International Metrological Organizations

In our case this refers almost exclusively

to national standardization laboratories of

other countries, since BIPM and other metrological agencies have little activity in

spectrophotometry. These laboratories both

supply and use techniques and data, and they

7
Key to Direct Transactions Matrix

Each intersection in the matrix in Table 1 contains an array of five numbers

which quantify our estimates of the interactions. The five keys in this figure

are arranged in the same pattern as the numbers in a given intersection. An

X in the intersection indicates that this transaction was deliberately not con- sidered, a ? in any position indicates insufficient information for a judgement,

and a ]_ in any position indicates insufficient information, but we are making a strong effort to get it.

IMPORTANCE

How important is this transaction in

terms of its economic worth or other

value such as contribution to health

or safety?

1 - Of minor importance

2 - Important or desirable

3 - No alternative or legally

requi red

4 - Essential

ADEQUACY

Is this type of transaction proceeding adequately?

0 - Yes

1 - Yes, but some improvement

is needed

3 - No, it is less than adequate,

4 - No, it is completely inadequate.

MAGNITUDE

What number of measurements or interactions

are involved, or what quantity of goods or number of services does this interaction

represent?

Blank - A negligible number or quantity.

1 - A rather small number of quantity.

2 - A moderate number or quantity.

3 - A large number or quantity.

4 - A huge number or quantity.

RATE OF CHANGE POTENTIAL EFFECT BY NBS

What word best describes the change

in the number or importance of the

transactions represented here?

N - Decreasing

0 - Not Changing

2 - Increasing

4 - Increasing very rapidly

With a successful program at NBS

of the magnitude proposed as a result of this study, what percentage increase in the potential

value (magnitude, effectiveness,

or importance) of this transaction would result?

1 - Little or no increase.

2 - A moderate increase

3 - A large increase

4 - A very large increase

8
General

Public

H rH

eg

CM OJ

rH CM

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eg on CM

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CM OJ Medical and ^

Health

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eg

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: reanizations X X X X X X X X X X X X X X X X X X

Knowledge

Community

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SPECTROPHOTOMETRY

MEASUREMENT

U

SYSTEM

S

INPUT-OUTPUT

E

DIRECT

R

TRANSACTIONS

S

MATRIX

SUPPLIERS

^

^

Knowledge Community

International

2

Metrological

Organizations

Documentary

3

Specifications

Organizations

,

Instrumentation

Industry

5

NBS

Standards

and

6

Testing

Labs

and

Services

Regulatory

'

Agencies

Other 8

Department

of

Defense

Other

Federal

9

Government

Agencies

State

and

Local

10

Governmental

Agencies

Industrial

11

Trade

Associations Appearance

12

Related Industry

,

Safety-Related

Industry

Food

lit

Production

Industry

Energy-Related

Industry

bD

OJ a

HJ -H O M

S C

CU CU CC CO

MO

rH

Medical

and

'

Health

n

General

'-°

Public

9
also supply measurement services and transfer

standards.

3. Documentary Specifications Organizations

These include the major ones such as ISO,

ASTM and ANSI and those committees of industrial trade associations which write standard

methods and procedures. It also includes

governmental and military organizations which

deal in specification and documentary standards. These organizations make use of data

and techniques in the general sense and supply

documented standard procedures and specifications based on spectrophotometric measurements.

4. The Instrumentation Industry

This is a key part of the measurement system. Most of the users are not in a position

to modify or improve their instruments, so that the state of the measurements is determined to a great extent by the instrument

manufacturers. The instrument manufacturers

make use of data, techniques, documentary

standards, and transfer standards to supply

instruments, related techniques, and standards. Many instrument companies also supply

consultation services on special measurement

problems.

5. NBS

In general, the role of NBS is similar

to that of the other National Standards Laboratories as indicated in category 2. Specific details of the NBS programs are given in section 4 of this Summary Report.

6. Standards and Testing Laboratories

This category includes all commercial and

governmental 1 aboratorei s , beyond the national

standardization laboratories, which supply

measurements as their services. Some of these

also supply documentary standards and, in such cases, would also be included in item 3 above. These organizations make use of

techniques, data and standards in their work.

7. Regulatory Agencies

The principal ones in this connection are involved in safety regulations governing the

performance of reflectors and warning signs

and governing color coding for safety signs.

Other regulatory agencies dealing with such

topics as health and communications also fall

into this category since they make use of

spectrophotometric measurements in enforcing

other regulations such as those governing

food additives.

8. The Department of Defense

In addition to its role in specification

indicated in item 3, and its internal standardization laboratories covered in item 6,

the Department of Defense makes great use of

spectrophotometric measurements in procurement and in research. This latter activity

provides a source of data and techniques for

the rest of the measurement system.

9. Other Federal Government Agencies

This includes such organizations as the

U.S. Department of Agriculture in both its

research and information clearinghouse roles,

the General Services Administration in its

procurement role, the Weather Service in its

data gathering operations, and the Postal

Service in its automated mail handling operations. These organizations take advantage

of techniques and data to provide services

which people often do not associate with

spectrophotometry.

10. State and Local Government Agencies

This category includes principally procurement of materials, e.g. reflective sheeting

for highway signs by transportation departments and paints by maintenance departments.

The extent of the direct use of spectrophotometric measurements by these groups

varies widely from location to location.

11. Industrial Trade Organizations

Many trade groups are included in connection with their documentary standards functions in item 3. In this section are included principally the instrument manufacturers' trade groups. These organizations

provide a key interaction point between NBS

and the instrument industry. One principal

contribution is their supplying data on the

performance of the measurement system through

laboratory intercomparisons.

12. The Appearance Related Industries

This is the first of several classifications of industries in terms of their particular connection to spectrophotometry. The

appearance related industries would include

all industries which make products for producing appearances such as the paint industry,

the printing ink industry, and the dye industry, and all industries making objects in

which appearance is an important factor. Such

industries include the textile industry, the

appliance industry, the automotive industry,

the printing industry, and the packaging and

advertising industries. The objects involved

10
range from spools of thread to railroad

trains, and includes foods to the extent that

their appearance is involved. These industries supply themselves with measurement

services and the public with a wide variety

of goods. They use instruments, standards,

and measurement techniques. Large industrial

organizations in this area often maintain

their own spectrophotometric laboratories,

the standardization and measurement service

activities of which are included in item 6. above.

13. Safety-Related Industry

This includes the industries making safety

related devices such as reflectors and fluorescent safety vests. These products are related in general to appearance, but a separate category is included here because

of a difference in the modes of interaction

with the other groups.

14. Food Production Industry

This grouping includes groups dealing with

food other than from an appearance or from a health-safety aspect. It includes a non- destructive testing of agricultural products

for nutritional content, ripeness, storeability, spoilage and the effects of disease.

These groups make use of measurement systems

to provide food which might otherwise not be

available for human consumption.

15. Energy Related Industry

This section emphasizes groups dealing

with the radiative transfer of heat and light

in order to make the most efficient use of

the energy sources which are available. The

principal item supplied here is energy transfer data and the principal users are architects and engineers within the same industry.

16. Remote Sensing

This quasi-governmental activity is listed

separately both because it is so large and

because it represents a cooperative effort

which crosses the boundaries of many groups

listed above. Its main requirements as a user are instruments and calibration services

and its service is supplying data for a host

of applications. Quantitative remote sensing

from space is almost entirely dependent on either radiometry or on spectrophotometry.

17. Medical and Health

In terms of spectrophotometry, the largest

transaction in this portion of the measurement

community is the one in which the clinical

laboratory supplies data to the physician to aid him in his diagnosis. Another part of

this segment is the drug industry in which

spectrophotometric measurements are used in

research and quality control.

18. The General Public

The general public includes individual

citizens and groups not included in the lists

above. Almost no private citizen performs

spectrophotometric measurement by means of

instruments for himself in the same sense

that he makes measurements of weight, length,

and volume with scales, rulers and cups in

his everyday activities. The closest the

average citizen comes to such measurements

are his "eyeball measurements" to determine

whether paints match, are the right color,

or are light or dark enough or whether the

window or wall in his house needs washing.

The average citizen is only indirectly con- nected with the more sophisticated spectrophotometric measurements and is, as he probably should be, usually unaware of their

exi stence.

In examining this input-output transactions

matrix, one must take into account the very

broad range of relatively disconnected groups

involved in each category. From row to row

in each column the entries often apply to entirely different user groups as well as to different supplier groups, and from column

to column in a given row the entries often

apply to different supplier groups. In the same way that spectrophotometry is a tool for

measurement among many for the typical user,

so the transactions listed are very complex,

involving more than spectrophotometric

measurements in carrying them out and more

than a change in the status of the spectrophotometric measurements to bring about a change in them. As a result, the matrix as

a whole and its individual intersections are even less meaningful than is usually the case

for such matrices. However, there are a few

points to notice.

a) The transactions in almost every category are increasing, not only because

of the general growth in the nation's

population and industry, but even more because of the increasing use of automation and sophisticated technology.

b) The general public is involved almost

entirely as a consumer of products,

and not as a consumer of spectrophotometric services. Therefore, the blocks

in the last column indicate public

consumption of objects on which people

make "measurements" based on their

ability to see and feel. Although

11
these measurements are crude in scientific terms, they are of the ultimate

importance in judging the success of

the more sophisticated spectrophotometric measurements used by the suppi iers.

c) None of the importance entries are "essential". This is simply because

there are alternative ways of doing

the job in almost every case, and mankind would survive if the jobs for

which there were no alternate method were not done. However, it would be

logically obsurd to discount one way of

doing a job simply because another

existed. The extreme value of spectrophotometric measurements is described

by "effective" not by "essential", for

in many cases the spectrophotometric

measurement is the most effective way

of doing a job.

d) With the exception of the field of

remote sensing, which is a field still

struggling with its adolescence, there

are no entries of 4 in the adequacy

column. In most other transactions

which have a longer historical background, ways have been found to even- tually get results. In almost every

case, however, there is room for significant improvement, and it is toward

such improvements that the NBS spectrophotometry program should be directed.

e) The groups in the upper left hand corner generally interact in both directions

with each other since they are all on essentially the same level in the system.

It is only as one gets to the consumer

level that the transaction is more or less one way. There is an indirect

return transaction by the consumer which

is not listed on the table because it

is difficult to quantify. That transaction is the acceptance or rejection

of a manufacturer's goods or services,

which in a vague sense is conveying

the results of sensual spectrophotometric measurements back to the manufacturer.

f) The lower right hand corner was coded

to indicate the way the new NBS program

is intended to interact with the mea- surement system. The regions marked

for the highest increase in potential

through NBS activities are those toward

which the program is directly aimed.

The regions with lower increase in

potential are those where the NBS program could produce either incidental

fallout benefits or else where the

influence of the NBS program is indirect.

2.5.2 Highlights re Major Users

The users in categories 12 through 17 are

the principal ones in terms of size. In order

to properly interpret the matrix, one must

visualize a jump in size of three or four

orders of magnitude in going from entry 11 to entry 12 in the table. All of the groups have

been described briefly in itemizing the categories in section 2.5.1. Because of the number and complexity of the major user groups,

they will not be described in further detail

here.

3. IMPACT, STATUS AND TRENDS OF

MEASUREMENT SYSTEM

The basic appeal of spectrophotometry as a measurement technique lies in the possibilities

inherent in an eye which can see in the entire

range of wavelengths from the far ultraviolet

to the far infrared; an eye which can accu- rately single out any desired portion or com- bination of portions of the spectrum for

scrutiny; an eye which neither tires nor blinks and which can make accurate quantitative judgements over many orders of magnitude.

To such an eye the possibilities for analysis,

inspection, and automatic process control are almost limitless.

Spectrophotometry is clean, allowing, for

example, chemical analyses to be performed

without the complexity of wet chemical techniques. Spectrophotometric instruments are easily automated and can be made quite simple,

making possible untended sensing stations

which relay to a central point data concerning

such phenomena as meteorological conditions,

pollution levels in air or water, or the

status of a product on an assembly line.

Spectrophotometry is convenient, since the

data can be obtained very rapidly and the

output of the detectors is in the form of

electric impulses or electric currents, either

of which are readily interfaced to electronic

analog or digital computers which can store

and analyze the data, make corrections, perform complex computations, and present the

results in a useful form.

Recent advances in technology add to the

appeal of spectrophotometry. Many improvements have been made in photoelectric detectors over the past few years, increasing

spectral range, efficiency, and stability

and reducing noise. The continual trend in

electronics has been toward reduction in size,

decreased noise, increased efficiency, and

greater gain so that the electronics need

hardly ever be a limitation to a measurement.

Digital computers have decreased in physical

size and cost to the point that it is possible

12
to include them as an integral part of even

nxiderately priced measurement systems, and

automatic data taking equipment and time

sharing computers extend this capability

to the lower priced systems. Smaller,

stronger, and more stable radiation sources

are available. Light emitting diodes and

solid state detectors offer new possibilities

for portable instruments. Tunable dye lasers

which can be operated in a quasi -broadband

mode appear to be an ideal radiation source

for spectrophotometry, providing power levels

which are completely impractical with an incandescent source followed by a monochromator. In addition to providing high power,

the advent of the laser has stimulated the

optics industry so that optical components

are better and more readily available than ever before. Thin film technology has made

rapid gains, offering many additional possibilities for producing special filters and

reflectors.

In response to the advances in component

technology and the ability to handle large

amounts of data and complicated data reduction schemes which is provided by computers,

a strong interest has arisen in developing

new instruments and uses for spectrophotometry. The projected increase in the rate

of purchase of spectrophotometric instrumentation by laboratories engaged in chemical

analysis alone is from 110 million dollars

per year in 1970 to 238 million dollars per

year in 1980, a rate which parallels the

overall increase in analytical laboratory

instrumentation. The potential for far more

dramatic increases, however, lies in areas

more closely related to the everyday world

such as automation of industrial processes,

quality control, routing of mail and freight,

inventory control, and crime detection. In such areas the possibilities for increasing

productivity, reducing confusion and drudge

work, and improving safety conditions through

spectrophotometric techniques are almost

endless

3.1 Impact of Measurements

3.1.1 Functional, Technological, and

Scientific Applications

In general , the measurements are used as an analytic probe. At one extreme is the

chemical analysis use, in which the reflected

or transmitted radiation is studied in terms

of what is missing, that is, how much radiation is being absorbed in the sample. From

this, one can deduce or monitor the chemical

structure or content of the sample. At the

other extreme is the appearance related

industry, in which the reflected or transmitted radiation itself is of interest. From

it, one can determine how an object will

appear under given lighting. In between lie

a large number of other uses, ranging from

automatic inspection for flaws in fabrics to determining the structure of ice sheets and

cloud formations from satellite observations.

In general, spectrophotometric measurements

are "eyes" of industry, but eyes which cover

a much wider range of wavelengths than human

eyes, and which are not as easily tired or prejudiced

The measurements are involved in almost

all areas of manufacturing and trade in con- sumer goods in which appearance is involved.

This includes printing, food processing, the

automotive industry, the printing industry,

the photographic industry, the textile industry, the paint industry, the building industry, and many others. It also includes

suppliers of these industries, such as the

dyestuff industry, the plastics industry, and

the manufacturers of pigments and inks. In the chemical analysis area, there is an extremely broad range of applications in

manufacturing. One aspect of chemical analysis, clinical chemistry, has a very large

impact, not only in terms of its monetary

worth (over $1 billion per year of clinical

tests depend upon spectrophotometric measurements) but in terms of its impact on the

health of individuals and communities. In addition, there are a large number of smaller

but very important areas in which spectrophotometric measurements play a role. Retroreflectance measurements are key in the production of safety reflectors and traffic sign

sheeting, which, while representing a relatively small fiscal outlay, play a large

role in safety. Spectrophotometric measurements also play a role in the automatic

inspection of bearing surfaces and the surfaces of other fine machine work, and the success of these measurements can have a large impact in terms of the lifetime and

reliability of the end products.

Spectrophotometric measurements are used

for automatic monitoring of the production

or presence of dangerous pollutants, in which

role they have a large impact on the safety

and comfort of the public. In their role in

non-destructive analysis of farm products

and in remote sensing detection of crop

disease, these measurements will have an increasing impact on the success of the

effort to feed the world's populations.

A large number of fields of science involve

spectrophotometric measurements. They have

long been indispensible to chemical research.

They are also used in studying the radiative

transfer of energy, an investigative field

which is taking on a new and larger importance

in an age in which energy conservation is

becoming more essential. With the advent

of remote sensing via satellite, the use of

spectrophotometric measurements for geological
studies, meteorology, and large scale botanical research has been increasing rapidly.

3.1.2 Economic Impacts - Costs and Benefits

The costs and direct benefits of these

measurements as they are done now were not

calculated as part of this study. The mea- surement system has been practically selfsustaining for many years, and the object of

this study was to determine the impact of

renewed NBS effort. However, a conservative

estimate would be that spectrophotometric

measurements are or can be used in industries

involving from one tenth to one half of the

gross national product. These measurements,

or their alternatives, are only one part of

many aspects of these manufacturing processes.

One would estimate the cost of the measurements in tenths to thousandths of a percent

of the total in each area, which, while large,

is not staggering. In order to determine the

benefits, one must remember that for most

spectrophotometric measurements, there are alternative techniques which could bring

about the same end. For example, chemical

analysis can be carried out to the point

where the human eye or an analytical balance

can be used to judge the results, and fabric

inspection and color control has long been

done by human observers and for the most

part still is. The spectrophotometric mea- surement must be thought of in connection

with its alternatives in any cost and benefit

analysis.

In this study, an effort was made to avoid

getting bogged down in the immensity of the

measurement system both as it exists and as

it might be, and to look at it from the point

of view of the gains which might be made by more active NBS involvement. NBS would be

completely over-extended if it went into

applications research on spectrophotometric

measurements, so it was assumed that the NBS

role would be strictly one of making more accurate measurements readily available, and

thereby increasing the potential for application. In some fields, alternative methods

are probably superior to spectrophotometric

techniques, and these fields were not studied

further. Actually, some positive benefits

could be gained by NBS's advising caution in

the use of spectrophotometry for these applications. In many other fields a spectrophotometric technique is more rapid, costs less,

and is more accurate than its competitors,

or at least it has reasonable potential to be so if the state of the measurement art

can be improved.

The benefits from improving the spectrophotometric measurement system can be very

great. In almost every case, the cost of the

instrumentation can be quickly recovered in

the case of a successful system through

increased productivity and reduced waste.

The cost of failing to make these improvements is simply that the advantages will not

be obtained.

Because the measurements are generally in

terms of the ratio of the optical behavior

of an object to that of a real or idealized

standard, metrication will have little impact

on the spectrophotometric measurement system.

The numbers are usually the same in any system

of measurement. Since many instruments in

the analytic field are already constructed in

metric dimensions, the secondary impact of

metrication in terms of instrument construction

and spare parts will be less than in many

fields.

With the proper metrological support,

spectrophotometry has a key role to play in

the future of industry, science, and technology. Several particular aspects of the

field which were accessible to analysis were

looked into and from these alone, it was estimated that there is a potential for real

benefit in terms of productivity and the

prevention of waste of almost two billion

dollars annually and this by no means covered

all of the field. (See Appendix R of the

original report, included here as Appendix C.)

The study has obviously shown the importance

of the field and clearly indicates where the

larger areas of potential benefit are. Even

if the estimate were ten times too high and even if only one tenth of one percent of the

potential were put to use, both of which are

on the outside edge of probability, it is

clear from this study that if NBS does its

job properly in this field, the approximately

$400,000 total budget (including overhead)

for its activity in this field is easily

justified.

3.1.3 Social, Human, Person-on-the-Street

Impacts

To the extent that the more effective use of spectrophotometric measurements increase

productivity and reduces waste, the benefit

in an economic sense to the person-on-thestreet is apparent. He can satisfy his wants

and needs without as much labor, thereby

giving him more freedom to shape his life

style. There are sociological and psychological benefits to having the appearance of

one's surroundings under better control. The

benefits to be gained from more accurate

medical analysis are apparent, as are the

benefits to be obtained from having safety

devices work properly. The person-on-thestreet is almost always well removed from

the measurements themselves, to the point

that, in most cases, he is completely unaware

of their existence. However this will not

prevent him from enjoying and making use of

the benefits derived from them.

14
3.2 Status and Trends of the System

A certain level of accuracy in spectrophotometric measurements can be readily

obtained without outside help by a competent

scientist or technician. To the extent that

these measurements can be used, they are being quite fully exploited. However, the more complex measurements and those in which

high accuracy is required are not as successful. What is required to promote these mea- surements to their fullest potential is careful study by workers with sufficient radiometric training to be able to recognize the

significance of the fine points of the

measurements, workers who can determine the

appropriate techniques and equipment for the

measurements, who will translate these into

equipment which can be used under ordinary

laboratory conditions and by the present

laboratory personnel, and who can provide

clear instructions and appropriate standards

to back those persons in their work.

There are several driving forces toward

change in the spectrophotometric measurement

system. As ms mentioned earlier, new technology is available which makes advances

in this field possible and attracts the

interest of inventors and scientists. How- ever, the strongest forces are the economic

and social ones which are behind the trend

toward automation in general. The constant

watching in quality control, chemical process

control, etc., is the sort of thing that the

unblinking eyes of spectrophotometric instruments do best. This type of work is usually

very tedious to the human observer, and he

tends to become bored, lax in his efforts,

and inattentive after a short time on the job. As a result, the human observer is costly and

few people see a future in training for a job

in which automation appears both possible

and imminent. The result is that as more and more applications of spectrophotometry are successful, the impetus for using them will

increase even more rapidly.

There is a negative force due to the historic development of the measurements. A number of years ago, when technology was not

as advanced as it is currently and when the

subtle difficulties in the measurements had

not been recognized, spectrophotometric

instruments were oversold in the sense that

they did not deliver the end results which

were promised. As a result, many companies

and individuals had an expensive bad experience with the measurements and, quite naturally, developed a reluctance for further experimentation. The availability of new technology,

coupled with the arrival of "new blood" on the management scene has dissipated a great

deal of this reluctance. However, the

subtleties of the measurements still remain

and it is important that this unfortunate bit

of history not be allowed to repeat itself.

4. SURVEY OF NBS SERVICES

4.1 The Past

Work in spectrophotometry began at NBS as early as 1906, and over the ensuing years a number of significant instrument developments,

basic studies, and publications resulted from

the program. Especially noteable were the

work of Taylor in the earlier developments of

reflectance measurements, and of Judd in the

related fields of color and vision. A number

of NBS workers left to form their own companies

to produce spectrophotometric instruments, an indirect benefit of NBS activity in the field.

A bibliography which thoroughly covers NBS

publications related to spectrophotometry

through 1970 and partially after that is

available in NBS Special Publication 393,

"Colorimetry and Spectrophotometry: A Bibliography of NBS Publications January 1906

Through January 1973", by Kenneth L. Kelley.

During the sixties, NBS acquired some excellent commercially developed spectrophotometers

and was able to provide a number of useful

measurement services for industry, the military, and other government agencies.

The principal weakness of the NBS program

in the recent past was that the capabilities

of the NBS group were not being developed to the point of sophistication required to bring

about the next stage of improvement in the

measurement system. As a result, NBS was unable to provide leadership to the measurement community which would enable it to take

advantage of the new technology that was becoming available in the late sixties. At

that time, for example, there was a call for

extremely accurate filters for use in calibrating instruments for clinical analysis.

The Spectrophotometry Section in the Institute

for Basic Standards (IBS) failed to respond

satisfactorily to this challenge, and a group

was formed in the Institute for Materials

Research (IMR) to develop the filters. As a result, SRM 930A, a set of filters is now

being issued with transmittance measured to nearly state-of-the-art accuracy by that

group. This has provided a partial solution

to the clinical chemist's problems, but only

a partial solution. The matter of standard

techniques is being addressed to some extent

by that group, but the question of improving

the instrumentation which is available to the

average user and providing measurement assurance was left as a need to be satisfied by

IBS.Early in 1970, NBS management recognized

that the IBS Spectrophotometry Section was

in trouble and placed it under Dr. R.P. Madden,

who 'served as Acting Section Chief while also

conducting the affairs of the Vacuum Ultraviolet Physics Section of which he vms Chief.

Under his direction, work was begun on the
first IBS reference instrument, one for measuring transmittance. In January 1971, the

Spectrophotometry Section was dissolved, and

its activities were placed in the Optical

Radiation Section. At that time Dr. W.H. Venable was placed in charge of the group

performing this work and began this study,

the principal part of which was completed in

1972.

4.2 The Present - Scope of NBS Services

4.2.1 Description of NBS Services

There are four NBS organizational units

dealing with spectrophotometry. Most of the

general work in spectrophotometry is done by

two of these, the Spectrophotometry group in

the Radiometric Physics Section of IBS and

the Spectrophotometry and Fluorimetry group

in the Special Analytical Instrumentation

Section in IMR. The activities of the IMR group are generally related to analytical

chemistry with the emphasis on measurement

of absorption and fluorescence. The activities of the IBS group are directed toward

radiometric and appearance measurements with

the emphasis on the measurement of reflectance

transmittance. Two smaller efforts are being

carried out in other parts of NBS. In the

Optics and Micrometrology Section of IBS,

there is a program for supplying transmittance

and reflectance step tablets in support of the

photographic industry. The activities of this

group are reported in the division summary

report of the study. The National Measurement

System for Optics . In the Laboratory Evaluation Technology Section of the Institute for

Applied Technology (lAT) in NBS, there are

several collaborative reference programs

involving spectrophotometry. These programs

provide wel 1 -controlled and regularly repeated

intercomparisons of laboratory measurement

capabilities in which individual laboratories

can participate on a subscription basis. A spectrophotometric laboratory is maintained by

this group for preparing samples and certain

standards which are used in connection with

this program. In addition, this laboratory

supplies reflectance standards on a regular

basis to the paper industry.

NBS participation has been strong in the

spectrophotometric activities of the CIE,

principally through participation in the

activities of Technical Committee TC 2.3

"Materials" which deals with those properties

of materials involved in radiative transfer,

particularly with respect to applications to lighting. Dr. Mielenz of the IMR group is

the chairman of the subcommittee on Fluorescense in TC 2.3 and Dr. Venable of the

Radiometric Physics Section of IBS and

Dr. Shumaker of the Optical Radiation Section

of IBS are both active participants in the

work of the committee.

Within the United States there is considerable NBS participation in committee activities directed towards standards and standard

techniques. The IBS group participates in

the work of the American Society for Testing

and Materials (ASTM) and the Inter-Society

Color Council. The IMR group receives con- siderable support for its work related to Clinical Chemistry from the American Association of Clinical Chemists. The lAT group,

through the activities of Dr. Lashof and

Mr. Hammond participates strongly in the work

of both the ASTM and the Technical Association

of the Paper and Pulp Industry. In addition

to this principal committee work, members of

all of the groups act as consultants for other

committees and associations which develop

specialized standard test methods.

The principal NBS activities at present

are developing instruments and techniques.

Since the former NBS Spectrophotometry Section

did not maintain a leadership role in the

measurement system, the instrumentation with

which NBS was left at the beginning of this

decade was only slightly above average. As

a result, in 1971 NBS was not in a position

to properly standardize the measurements at

that time, much less to help provide improvements. The IBS Reference Transmittance

Spectrophotometer which was started in 1970

by Dr. Klaus Mielenz working under Dr. Madden

has been fully automated and is now operable

in the ultraviolet and visible portions of

the spectrum. An attachment by means of

which this instrument can measure specular

(mirror-like) reflectance has been constructed

and awaits testing. A reference instrument

for making directional incidence, hemispherical

collection measurements under a wide variety

of conditions has been constructed. That instrument has been sucessfully used to resolve

the discrepancies between the absolute reflectance measurements of several national laboratories. Several measurement accessory systems

have been designed and constructed to be used

with the same instrument which provide a capability for bidirectional measurements of

diffuse reflector, specular reflectance

measurements, and the measurement of diffuse

reflectance and transmittance, all with very

high accuracy. Arrangements are under way

at this writing for providing several secondary

standards laboratories with master standards

measured with this instrument. IBS has also

constructed, with the help of funding from

the Consumer Product Safety Commission, a reference instrument for retrorefl ectance

measurements, which will be used for a number

of applications related to safety. Two

reference instruments have been built by

the IMR spectrophotometry group. The first,

built by Dr. Mavrodineanu, is a reference

transmittance spectrophotometer designed

16
especially for developing and calibrating

standard filters and solutions for absorption

spectrophotometry. The second, built by

Dr. Mielenz, is a very versatile goniospectrofluorimeter. The principal remaining

gap in NBS reference instrumentation for

spectrophotometry is in the moderately long

wavelength infrared region of the spectrum

from 2 to 50 micrometers. Plans are under

way in the IBS group to provide instrumentation in this spectral region. With this

reference instrumentation, NBS is again

assuming the role of leadership which it

should have in the field of spectrophotometric

measurements.

In the area of general purpose standards,

the IBS spectrophotometry group has been

currently working through the Office of

Standard Reference Materials at NBS to supply

as Standard Reference Materials rare earth

glass filters for calibrating wavelength and

white glass standards of diffuse reflectance.

These materials, which had formerly been

issued with little or no documentation as to their proper use, will be supplied with complete instructions including corrections for

different instrument parameters such as bandpass and beam divergence, when needed. Work

on supplying diffuse reflectance SRM's and

replenishing the supply of standard mirrors

in SRM is now under way in the IBS group, and

this group is also developing standard retroreflectors as a potential SRM. The IMR group

has developed and is supplying standard filters (SRM 930A) and solutions (SRM 931) which

are used principally for calibrating and

checking the performance of absorbance spectrophotometers for analytical chemistry.

Standard filters for use at ultraviolet wavelengths and standards for measuring fluorescence are currently being developed by that

group.

As the new NBS measurement capabilities

are developed, means are being developed to use them to serve the scientific and industrial community. The support of groups in

industries, in universities, and in other

government agencies is being used in this

work. In summary, the NBS spectrophotometry

program is currently in a state of transition.

It currently supplies a fair amount of con- sultation (an average of one call per day)

and a very modest amount of measurement ser- vices and standards, principally aimed at

developing improvements in the measurements.

Efforts are being made to take full advantage of every contact with the measurement

system as a whole in order to be able to make

the best possible use of the new NBS measurement capabilities as they are developed.

4.2.2 Users of NBS Services

The users of NBS services fall into three

general categories: (1) instrument manu- facturers and secondary standards laboratories,

(2) people working in research both in industry and in universities, and (3) people performing industrial and laboratory testing

measurements on a routine basis. Because of

the changes in the spectrophotometry program

at NBS, discussion of the users will be

deferred to section 4.5 which deals with the

future.

4.2.3 Alternate Sources

In terms of the quality of the measurements, until recently almost any of the

present NBS spectrophotometric Standards

could be supplied by one (but not more than

one) other of a number of good laboratories

in each area of the measurement system. The

reason is that the NBS measurements in the

past have been made on commercial instruments

for which there are unexplored potential sources of systematic error. Therefore, any

one laboratory could also supply standards

with a given systematic error. There would

probably be no trouble until two laboratories,

each with its own source of systematic error,

began to supply standards. In terms of a few arbitrary requirements for traceability

to NBS, some users are forced to go to NBS,

but beyond that, alternate sources could

supply measurements at that level. However,

because of the highly dispersed nature of

the measurement community and the sophistication of the instrumentation and techniques

required to standardize spectrophotometric

measurements at their optimum level, it is

very doubtful that any source other than

NBS could effectively improve on the present

state of the measurements.

4.2.4 Funding Sources for NBS Services

The funding for the present NBS spectrophotometry program has been largely from NBS

STRS (in-house) funds. The principal exception is the work related to clinical chemistry

in IMR. In the past, a larger fraction of

the funds of the Spectrophotometry Section

came from contracts from other government

agencies. However, the principal product of

the work done under such funding was data on specific samples, and this funding in general

did little to advance the ability of NBS to serve the measurement system. With regard

to these agencies, NBS was a measurement

service laboratory. Since 1971, outside

17
funding has been discouraged, except for

special cases in which it is felt that it

would advance the NBS measurement capability.

An example of this latter case of the clinical

chemistry work in IBR and the Consumer Product

Safety Commission's support of the IBS development of a basic capability in retroref1 ectance

measurements. When it is justified in the

interest of the national measurement system or because of the uniqueness of the NBS facilities, measurements are occasionally performed

at NBS at cost for industries and other agencies and standards and standard reference

materials are also sold to cover the cost

of the routine portions of the measurements.

4.2.5 Mechanism for Supplying Services

Services are supplied principally through

three mechanisms. The first is the standards

and measurement services which have already

been mentioned. The second is through con- sultation about measurement problems and

techniques directly with users, principally

those who are engaged in developing new applications of measurements. When a new application is promising, the NBS groups sometimes

supply measurement assistance to enable a worker to determine what wavelength range or type of measurement he should employ for his

purpose. The third way is through working

directly with instrument manufacturers, com- mercial consultants, and commercial measurements laboratories. NBS personnel work with

the staff of these organizations, both on a one-to-one basis and through their trade

associations, in order to help raise the

quality of the instruments, standards, and

services offered by them. This portion of

the measurement system is judged the most

productive one through which NBS can supply

its services, since each of these groups in

turn influences the rest of the highly dispersed measurement community in a way in which

NBS alone could equal only with much more

effort. In a sense, NBS uses these groups

as a multiplying agent for its efforts while

at the same time assisting them in their

efforts.

4.3 Impact of NBS Services

4.3.1 Economic Impact of Major User Classes

As has already been mentioned in section

3.1 of this report, the economic impact of

the major user classes includes a very large

fraction of the gross national product. This

impact has not been evaluated, but an effort

has been made to evaluate the potential worth

of improvements in the measurements, which

potential worth may be as high as $2 billion

per year if full advantage is taken of the

improvements. In addition there are benefits

in terms of health and safety which can be

realized but which are difficult to give a monetary value. The NBS services of the

recent past did little to make these improvements possible, and the present efforts at NBS are directed toward enabling NBS to assume a role of leadership in providing

these improvements. The present NBS impact

is still quite small, although it is growing,

but the major NBS impact will occur in the

future.

4.3.2 Technological Impact of NBS Services

The technological impact of the NBS ser- vices is indirect. Because of the immense

size of the user community, the direct impact

of NBS services will always be relatively

small. However, the catalytic effect of the

NBS instrument development assistance and

measurement assurance efforts can provide a great impact in the future.

4.3.3 Payoff from Changes in NBS Services

In order to gain time, outside agencies

have been discouraged from seeking routine

measurement services from the IBS spectrophotometry group. The impact of this change

has been small, since more and more commercial

instruments with capabilities equal to NBS's

commercial instruments have reached the field

and since the standards provided by the instrument manufacturers have been of nearly as good quality as those which were offered by

NBS in the recent past.

The principal change for NBS has been to direct its services toward the instrumentation industry through measurement assurance

programs and other direct assistance at the

level above that of the large body of users. Only a very small portion of these programs

are in operation yet, and the lag time from

inception to payoff can range from five to ten years. As a result, the evaluation of

the payoff for these changes must be judged

in the future.

4.4 Evaluation of NBS Program

The principal characteristic of the present

NBS Program is that it is in transition. The

program which is being set up is distinctively

different from that in the past, and, as a result, it is too early to be able to judge

the strengths and weaknesses of the program.

The needs for NBS services have been determined principally in the study conducted in

1971 and this determination has been con- stantly updated through contact with workers

in the field. The stream of calls for con- sultation and measurement which NBS receives

provides an automatic source of information

which provides about half of the input needed
to keep up to date on the needs for standardization services. The other half of the outside information is obtained through direct

inquiry of those working in an area where a suspected need exists and through working

meetings of standards groups and trade

associations

The present NBS sources are, as noted,

inadequate to meet the challenge of the need

to increase measurement accuracy at the user

level, except in the area of regular transmittance. In those few areas in which NBS

has adequate resources, at present priorities

among users are assigned on the basis of

highest multiplying power, i.e., which ser- vices are most valuable in the long run toward

building up the measurement system. "Valuable"

in this case may be in terms of feedback to NBS to help determine what is needed or "valuable" may be defined in terms of the user's

ability to spread the benefits of NBS's

service to him through the measurement community. As a result, most of the NBS ser- vices at present, with the exception of con- sultation, are directed toward the instrument

industry and commercial and military measurement laboratories. The main exception is with

respect to consultation, where listening to and helping users at all levels continues to

be a valuable source of information about the

spectrophotometric measurement system.

It is highly feasible to "contract out" the

standards work in the sense of having standards issued by other laboratories which

receive measurement assistance from NBS. In fact, this is the direction which should be

taken. Likewise, most of the measurement

service requests which come to NBS can be

handled by other laboratories, so that NBS

services should be limited to those with some strong measurement system "payoff".

The role which is being shaped for NBS is one which is clearly within the mandate of NBS

and which should be unique. It is within the

NBS mandate because it is a measurement

standardization problem. Because of the highly dispersed nature of the user community it

is probable that an adequate program to meet

the challenge of spectrophotometric improvement can not be organized anywhere else.

Furthermore, because of the expense of realizing the type of capability which is required

to advance these measurements, it is highly

desirable that this effort be done centrally

and not duplicated. Thus this work should be

done mainly at NBS.

4.5 The Future

Actually, throughout this report it is

really the future which is being addressed.

The anticipated needs for improvement in

accuracy amount to reducing the error by

approximately an order of magnitude in almost

every area of spectrophotometric measurement.

The sort of instrumentation and expertise

required for this sort of work would be

prohibitively expensive for any user when

viewed in proportion to the part spectrophotometry plays in his overall program.

However, there are so many users that a relatively small program at NBS can lay the

foundations for immense benefits.

The impact of the National Measurement

System Study on this NBS program has been

immense. This is natural, since this particular study was initiated on the recognition

that there was something wrong with the NBS

program at the time. As a result of this

study, a radical change has been brought

about in the NBS program for spectrophotometry

which should make it very effective with only

a modest additional initial outlay of funds

during a five year re-instrumentation program.

Continuing impact assessment and other

evaluation of the measurement system is

built into the way the program is conducted.

5. SUMMARY AND CONCLUSIONS

The National Measurement System in Spectrophotometry is currently far from living

up to its potential value. A rapidly

developing technology supports improvements

in these measurements and provides the

material with which to develop these measurements to their full potential. A relatively

modest program in NBS, augmented by active

cooperation with instrument manufacturers

and commercial 1 aboratorei s , can provide the

measurement support which is required for a much fuller realization of the benefits to

be derived through spectrophotometry. NBS

should proceed with all deliberate haste to meet the challenge of this potential.

19
A-1

APPENDIX A. METHODOLOGY OF THE STUDY

The methodology of this study was chosen to fit the situation in which

a lone investigator must probe a huge measurement system in which there

exist really very few specialists and determine what NBS should do. The

decision was to pursue a rather small number of representative samples of

the field in depth, rather than make a shallow pass at the entire field.

The approach was quite simple. The records of the old Spectrophotometry

Section were scanned to determine which fields were being served in the past.

The Thomas Register and similar references were searched for representative

samples of each type of user, and a list of these was made up. From these

lists were planned a series of visits to these industries and laboratories

based, principally, on geographic location. After several trips, certain

of the fields were eliminated from the list as being ones for which the

present measurement system was adequate. In the other cases, the visits

were continued until sufficient understanding of the nature of the problems

was obtained. As the study progressed and new fields of use were come upon,

they were treated in the same way. The timing of the trips was planned in a way to allow attendance at as many relevant professional meetings as possible.

At such meetings, the connection between the activities of these groups and

the National Measurement System were observed. After a year and a half of

such travels, punctuated by accompanying periods of literature search, three

conclusions about the measurement system as related to NBS became apparent:

1. There was an immense potential value to be gained by providing

improved spectrophotometric measurements, annual dollar value of

which is ten thousand times the cost of the NBS program.

,2. This potential would be so difficult to realize without leadership

by NBS that the probability of its being realized through any

other means was extremely low.

3. There is an approach, through reprogramming , by which NBS can supply this leadership without significant increase in funding. Once

these three conclusions were reached, the cost effectiveness of further

formal study of the measurement system dropped to nearly zero. Therefore,

the results of the study were put into the 1972 report for IBS management

and the formal study was ended. In short, the needs have been identified,

they are great, and it is time to get on with the work. However, the

National Measurement System in Spectrophotometry continues to be evaluated

as a natural result of the pursuit of the NBS program.

20
B-1

APPENDIX B. A PROPOSED DIRECTION FOR NBS EFFORTS

The following is section 7 of the report from the 1972 IBS study. It

sunnnarizes the rationale behind the current IBS program. With certain

exceptions involving the emphasis on standards and the source of funding,

it reflects the type of thinking behind the basic work being done in spectrophotometry by the IMR group as well.

7. WHAT SHOULD NBS DO?

Since there is no basic unit such as length or electric charge to be

maintained in spectrophotometry, there is sometimes a tendency on the part

of those not familiar with the field to assume that there is no need for

IBS activity. However, in reality it is not sensible to expect that correct

spectrophotometric measurements will occur unaided if the ratios have been

defined, just as it is not sensible to assume that length measurements will

be made correctly simply because the number of wavelengths per meter has

been defined for an atomic emission line. The mission of the Institute for

Basic Standards, as put forth in Department Organization Order 30-2B,

November 16, 1970 is:

The Institute for Basic Standards shall provide the central

basis within the United States of a complete and consistent

system of physical measurement; coordinate that system with

measurement systems of other nations; and furnish essential

services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry,

and commerce.

The United States clearly does not have a complete and consistent system of

measurement in spectrophotometry, and a great deal of assistance from a central agency will be required before the measurements will be adequate

for most of the scientific, indistrial, and commercial community. There is

clearly a need for an CiCJti\J<l program in spectrophotometry. The general

nature of such a program will be discussed in this section. Details of

the program are also given in certain appendices. In particular, since the

present activities of the group are the beginnings of this program, the

discussion in each subsection describing a recent or current activity of the

group in Appendix L (not included in the present report) provides insight

into the nature of the program being proposed.

21
1 B-2

7il THE GEERAL GOALS of the spectrophotometry program are to:

711.1 DEVELOP UiJIFORfl BASES spectrophotometrlc measurement. Since a spectrophotometric measurement is a determination of a ratio, the basis for

measurement consists of a definition of the ratio to be determined. In most

cases , these ratios have not been defined carefully enough to allow for future

improvements in the measurements, and in some cases there is no common definition at all. The definitions should be based on very general idealized

physical abstractions in order to avoid placing arbitrary restrictions on instrument design, but at the same time the properties so defined must be

measurable in practical ways and the quantities obtained must be useful to

the technical community.

7.1.2 BUILJ] UP SPECTROPHOTOfeRIC COTPETBICE AT ['JBS to a much higher levei

than before. We must develop the instruments and procedures for highly

accurate measurements in order to properly realize and maintain an absolute

measurement scale, and we must build up a better understanding of the physics

behind the measurements and the uses to which they are to be put in order to

define the measurements and provide adequate leadership to the technical

community.

7.1.3 EXERCISE LEADERSHIP in promoting accurate spectrophotometric measurements. It is quite clear that no all-encompassing organization of the diverse

users of spectrophotometry will form, either spontaneously or through persuasion,

to take the lead in spectrophotometry and define the needs for NBS. Rather

the spectrophotometry group in IBS must take an active role in seeing that

sufficiently accurate measurements can be carried out.

From the general goals outlined in the preceding paragraphs and the

state of the measurement system as it now exists, a general

7.2 DIRECTION FOR SPECTROPHOTOfHRY, described briefly m the following

paragraphs, has been worked out. It provides guidelines by which decisions

to undertake specific actions will be made. Examples of such actions are given

in Appendix I.

Competent pursuit of the spectrophotometry program will require much better

7.2.1 IllSTRUflB'jTATIQI than has previously been available to the group. The

general goals for the first phase of the program are to be able to make the

following general measurements on selected gage materials:

a. Specular transraittance to an uncertainty of 10"^

units of transmittance or .2% of the transmittance

value, whichever is larger,

b. Directional-hemispherical reflectance and transmittance to an uncertainty of 10"^ or .5% of the value,

whichever is larger.

22
B-3

c. Bi-directional reflectance factor to an uncertainty

of .5 =< 10"^ or 1% of the value, whichever is larger,

(All of the above are to be in the wavelength range 250

to 2000 nm, but realized initially in the visible range

from approximately 400 to 750 nm.)

d. Fluorescence measurements which will allow

determination of the transfer of energy from one wavelength to another with an uncertainty of less than 5%,

and

e. Infrared directional-hemispherical transmittance

and reflectance over the range 1 to 50 um to an uncertainty of .5 X 10"^ or 2% of the value, whichever is

larger

The accuracy limits given above are based on the present needs of a large

part of the users and on the current state of the art in sample preparation.

The IBS instruments themselves should be stable enough and well enough defined

to allow us to be sure that they contribute a relatively small part of the

overall uncertainty.

To be able to perform such measurements will require substantial

improvements on our present instrumentation and the construction of several

high quality reference instruments by means of which the measurements can be

placed on an absolute basis. Also, investigating potential sources of systematic

error in detail will require a flexible automatic experiment control and data

gathering system to handle the detailed measurements which will be involved.

The instrumentation itself should reflect the IBS role in the measurement

system. It should be flexible in order to meet the changes which occur on the

technological scene. It should be developed in such a way that parameters can be varied conveniently in order to investigate for systematic errors. Auxilllary

equipment such as would be used for mapping beams of radiation will be called

for. Such instrumentation would enable the spectrophotometry group to measure

definitively in a way which would be impossible for individuals in the various

segments of the technical community. The same instrumentation could be used

efficiently for investigating the common areas of diverse measurements, as,

for example, similar mapping techniques apply to studying the uniformity of

filters, reflecting surfaces, fluorescing materials and the spread of light

in translucent materials. A more detailed description of the instrumentation

to be developed appears in Appendix M. (Not included in the present report)

A carefully planned and strong

7i2i2 IflTERACTIOf^ with the technical and scientific community is essential if

the IBS spectrophotometry group is to carry out its mission successfully without

doubling or tripling in size. These interactions must be carried on at several

levels.

23
B-4

a. We must have a close working relationship with the

instrument manufacturers in order to be aware of the

measurements which are being attempted in order to assist

in reducing measurement errors which are instrument

related. In this latter respect, we might maintain certain special gages which could be loaned or rented to

the instrument manufacturers for testing their instruments, making gages available which would not be practical

to produce in large numbers. Such gages might for example

be filters which have nearly equal transmittance but differ

in their reflectance, thickness, scattering, or other

properties

b. We should work with secondary standards laboratories

to assist them in issuing gages which are adequately

documented and accurately measured. This would involve

checking the materials for suitability, measuring the

master gages, working with the secondary lab to see that

its transfer of measurement is proper, and occasionally

checking the laboratory's output. The gages issued in

the past by IBS have been measured by comparison to

master gages and could have been issued as well by any

of several secondary laboratories with our cooperation.

It should be noted that gages for evaluating the purity

of materials and other special purposes may best be

issued by IMR or possibly by lAT rather than by an agency

outside NBS, in which case IBS would provide measurement

support similar to that supplied to secondary standards

laboratories. In any case, IBS should concentrate on measurements primarily, and should not become involved

with developing gages. One important exception to this

would be in seeing to it that suitable materials for

certain general purpose gages are available. This might

even include direct action by our group to procure and

distribute to secondary labs certain hard-to-get materials

in cases where no other organization can handle the job.

c. We should work with the many organizations and

committees which are dealing with problems in spectrophotometric measurements, and particularly we should

become strongly involved with the bodies such as ANSI,

ASTM, ISO, and CIE which are determining general test

procedures. Our involvement, however, should be limited

to a technical nature, such as in assisting with definitions

of the properties to be measured and testing the dependence

of measurements on certain parameters. We should generally

avoid assuming such positions as committee chairman or secretary, because such positions include much administrative work and would spread us too thin.

24
B-5

d. We should interact through publications to promote

accurate measurements. This should include "trade

journals" as well as the scientific journals such as

JOSA. and Applied Optios . The natural tendency is for

measurements in each industry or technical field to drift

toward its own separate gage system. This results in the

inability of others to take full advantage of the results

of work which has been done in a particular field. This

tendency can be countered in publications both negatively,

by calling attention to departures which exist, and

positively, by providing information about correct procedures, about help which is available through IBS,

secondary standards laboratories and instrument makers,

and about pitfalls and limitations in certain types of

measurements

e. We should follow up indications of difficulty within

the measurements system. Sometimes these indications occur

in the course of commerce when difficulties in meeting

specifications are encountered. At other times organizations carrying out intercomparisons encounter discrepancies.

In general, however, only a detailed investigation requiring

specialized instrumentation can get at the basis for such

difficulties. This type of investigation when carried through

to the source of the trouble is probably the most fruitful

means of getting the measurement system in order. NBS is by

far best suited for such investigations both because of the

special instrumentation required and because of the detached

or neutral position which we can take in interacting with

parties of opposing interests.

Whenever possible, the IBS group should take an active role in seeking

out such interactions, rather than wait until we are approached. This active

role has several advantages. By discovering problems early, we can prevent

diverse scales of measurement from becoming entrenched within the data base.

By simultaneously seeking out problems in several fields using similar

measurements, we can develop standard techniques which have more universal

application. By actively seeking problems at a time when our instrumentation

is set up to handle a certain type of measurement, we can make more efficient

use of our time. By working with groups as they develop standard procedures

and by actively seeking to correct the faults in existing standard procedures,

we can prevent the propagation of poor or mis-applied procedures. It is throu,

taking an active role that the leadership which should be shown by NBS can be

exercised

25
B-6

Special steps must be taken to assist users in

7.2.3 APPLYIl^G IHE RESULTS OF BASIC RESEARCH to spectrophotometric measurements

at a practical level. Although a great deal of very basic research can be done

in the physics of absorption, scattering, fluorescence, transmission and reflection of radiation, and properties of gage- materials, this type of work should

not be undertaken in general at first. These fields have been extensively worked

over in the past, and there are other groups working on them at present, so that

there is much information available and more being provided continually. However,

there is a definite need to relate this basic information in a very pragmatic

way to spectrophotometric measurements. The principal research and theoretical

development efforts of the IBS spectrophotometry group for some time to come should be directed toward satisfying that need. Our initial basic physical

research should be directly supplemental to the applied research, filling in

gaps where information is not currently available, and it should be undertaken

with extreme caution so that it does not become the principal occupation of the

group. After the gap between theory and practice left by the former spectrophotometry program has been closed, the pursuit of basic physical investigations

can be reexamined.

Since spectrophotometric measurements are many- dimensional and the problems

of planning a measurement and evaluating the data are quite severe, means should

be developed by which the information most needed for an application can be

readily obtained. One of the most interesting and important aspects of applied

spectrophotometry is the question of how much spectrophotometric data must be

obtained, at what wavelengths, and how good must it be in order to determine

the value of the related parameter in which one is really interested, such as the concentration of a solute in a solvent, the amount of a particular colorant

in a paint pigment, what kind of soil or vegetation appears in a given part of an aerial photograph, or how well a given set of gages can be used to evaluate the

performance of a tristimulus colorimeter. The mathematical bases for handling

this problem are well developed, lying principally in the fields of statistics,

information theory, and functional analysis. However, with the exception of

statistics, very little has been done to put these mathematical tools in the

hands of the person solving the day to day problems of industry. An intermediate

step is needed between the esoteric product of the mathematicians and the myriads

of everyday problems which arise in applied spectrophotometry. This intermediate

step involves determining which theorems are applicable to evaluating spectrophotometric data and how, and then developing and explaining procedures by which

the practical problems of spectrophotometry can be handled in a way useful at

the applied level. In earlier times, this intermediate step would have been

almost of academic interest only, since the amount of calculations to be performed

in any but the simplest treatment would have been prohibitive. Only a few analog

techniques such as using weighting filters, as in tristimulus colorimeters, or simply electronic differentiation and integration were available for practical

handling of more than a few data at a reasonable rate. With the present ready

availability of digital computers and automatic data gathering systems, the

burden has been shifted to the mathematical analysis. In order to effectively

evaluate our own efforts as a standards laboratory, we must develop and apply

such analysis ourselves. Putting this analysis in a form which is understandable

and useable by the rest of the scientific and industrial community is one of

the most important contributions we can make.

26
b-7

The type of applied research described above should initially be used to

investigate spectrophotometric measurement 'czv se , in order to provide explicit

definitions of the quantities to be measured, evaluate natural limits of accuracy

and sources of error in present methods of measuring these quantities, and

developing better measurements for the future. The results of this research

should be published in a way that they will be of value to even those whose

background in optics and mathematics is relatively unsophisticated.

Our general goals strongly affect which

7i2i^ [EASUREJ'tlfrS undertake. We should avoid routinely issuing standard

gages, and in general, except for certain measurements made for groups within

NBS and other government agencies, we should only undertake measurements which

are directed specifically toward extending or improving the measurement process.

This is a distinct departure from the policy of the former Spectrophotometry

Section, but it is essential if we are to advance the measurement system.

The emphasis here is on the reason behind the measurement rather than the

measurement itself. For example, we might measure the reflectance of foliage

to help an agricultural laboratory set up general methods for measuring foliage,

but not simply to supply the laboratory with data on the reflectance of specific

samples of foliage. We should undertake color measurements to determine how

accurately a particular type of color measurement is being done, but not to

provide a routine colorimetric measurement. We should make measurements

in case of trade disputes regarding specifications, not simply to resolve the

dispute but to get at the basic source of the descrepancy. We should make

the results and outcomes of such measurements available to those making similar

measurements through publications and, when necessary, through direct mailings.

In this way, the greatest use can be had from the relatively small number of

measurements which a group of our size can do while continuing in the other

tasks listed in this section.

The final question of the program which the IBS spectrophotometry group

undertakes is the means by which the

7,3 SUPPORT program is to be provided. The present indications are

that the program should be supported between 80% and 90% directly from NBS.

The reasons for this lie within the nature of the program. The principal

need for direct support lies in the need for our keeping the

7,3il li'ilTIATIVEi is emphasized in the preceding section, we are to lead

towards an improved measurement system, we must be supported internally in general

The direction the work takes is rightly decided by those providing the support.

If we provide our own support, we can direct our own program. We can much more

effectively influence the measurement system by volunteering those general

services we feel to be necessary at a given time than by waiting to be called

in as paid consultants.

7i3i2 EFFICIENCY depends upon internal support for three reasons. First, in

losing the initiative in what we do we lose the advantage of scheduling our activities efficiently. Second, the time spent in negotiating contracts for

complicated undertakings is completely lost to doing the more important technical

work. Third, most contracted work is toward a specific end result other than

improving the capability of the group or the measurement system as a whole.

As a result, we would divert our efforts from our principal tasks.

27
B-8

Finally, a very practical

7i3i3 REALISM calls for this type of support. The structure of the measurement

system is such that approach to NBS regarding these measurements is voluntary.

It would be cumbersome to the point of impracticality to try to legislate proper

spectrophotometric measurements in the same sense that measurement of mass and

length are legislated. Nevertheless, since these measurements are so universally

used, the general public which pays for NBS and whose health, safety, and

satisfaction depends upon them is entitled to have the best measurements possible

in this field. It is highly unrealistic to expect the relatively few standards

laboratories with which we deal to altruistically volunteer to support the

system for the benefit of the general public. Neither will those involved in

a dispute over satisfaction of specifications be interested in supporting

general research into the basic causes of their difficulty as it affects the

rest of the technical community. It is also quite unrealistic to expect those

dealing strictly with us in the next five years to absorb the cost of catching

up with nearly fifteen years of NBS neglect of the fundamentals of spectrophotometric measurements.

Direct charges should be made for direct or "service" measurements for

other government agencies or other NBS groups. Such measurements have other

end objectives than improving optical radiation measurements. Charges should

be made for IMR and lAT master gage and other measurements which are covered

by sponsors or are catalog measurements, but the cost of intercomparisons and

other measurements undertaken for improving the measurements of both groups

should be internally supported by each. Charges should be made to secondary

laboratories to cover time spent directly on gage measurements and for routinely

maintaining the capability to perform these measurements, but we should not

charge for developing our capability to perform them. Likewise, in undertaking

specific tests, we should charge for the direct measurements only as they are requested by the "customer", and we should not charge for developing the

capability to make measurements or for services rendered to the rest of the

technical community as a result of our undertaking such measurements.

Under the foregoing guidelines for the support of the program, the bulk

of the financing must come from within NBS, particularly during the major instrument development stages. The benefits to the public are extensive enough and

general enough to justify supporting most of the work directly.

Once the program outlined in this report is undertaken, the magnitude of

the job to be done indicates that at least five years should be allowed to

pass before a major

7 A REVIEW OF THE PROGRAf'l be undertaken. However, after that time a reassessment

of the situation would very probably be advisable.

28
c-1

APPENDIX C. EVALUATING THE BENEFITS OF IMPROVING SPECTROPHOTOMETRIC

MEASUREMENTS

The following is Appendix R from the 1972 IBS Spectrophotometry study

report. It represents an honest effort to evaluate the worth of improving

measurements which are only partial contributors to an overall industrial

or commercial application. Several points of possible overlap and double

counting and one mistake in arithmetic in R.2.4 have been pointed out by

Dr. Howard E. Morgan, an economist at the National Bureau of Standards.

Dr. Morgan also pointed out that in some cases, the financial benefits

would probably be diverted from the directions indicated. However making

changes in this section would neither reduce the uncertainty in the final answers significantly nor increase the value of this section as an exercise

in evaluating the need for improved spectrophotometry.

Arithmetics of Relevancy and Impact

As the principal worker in the survey of spectrophotometry, I have

come to the conclusion that the present spectrophotometric measurements

should and can be improved, that NBS should contribute to these improvements.

This entire report has been intended to show the reasons for this conclusion

and to indicate how we plan to make our contribution.

However, most of the discussion up to this point has been qualitative.

Since a definite amount from public funds will be required to operate this

program, it would be appropriate to

R.l QUAI^IFY THE BENEFITS to be received by the public. When viewed from

a quantitative standpoint and directed toward a complicated program, a question

such as "What are the economic, social, and/or political implications?

(Consider 5-10 year projections)" is obviously so general and ill-defined

that it cannot be answered directly. What is an economic or social

implication? How far into politics should measurement standardization

extend? How does one define a benefit, and if one man's benefit is another's

detriment how should this be handled? All of these questions involve so many

value judgments and definitions that rational generalizations are impossible

in all but the simplest case.

When this report was first planned, the aforementioned complications

made attempts at quantitative descriptions of benefits appear impossible.

However, it became apparent during the course of the study that quantitative

estimates could be made in specific ways in

Ri2 SPECIFIC CASES^ ^nd that these specific estimates could be presented

along with their individual rationale for the reader shimself to evaluate

for worth as he sees fit. This procedure is analogous to the way mathematicians

define arithmetics. All that is required in their case is careful definitions

of the ground rules and operations and self-consistent arguments. Thus

1+1=2 or 1+1=0 depending upon whether common decimal arithmetic or single digit binary arithmetic is being used. The value of the arithmetic

depends upon the interpretation of the user and the application to which it

is put.

29
Since this presentation of some "arithmetics of relevancy and impact"

has been added almost as an afterthought, several of the contributors were

not included in the list of contacts since they were contacted so recently.

Therefore, their help will be acknowledged at the end of the subsections

to which they contributed. The numerical data, when not otherwise noted,

is based on interpretation of Bureau of the Census Data. If the actual

facts could be ascertained, it is highly unlikely that the figures differ

by as much as a factor of 10 from real life. The examples given should

illustrate why meaningful generalizations are difficult to make and yet

should indicate in specific cases the value of the proposed spectrophotometry

program.

R.2.1 EXAMPLES FRai THE PAIflT INDUSTRY

NOTES! The paint industry is highly dispersed, with 1500 companies

competing for $3 billion in business. The top eight companies

supply 36% of the product by value and the remaining production

is spread among the others. As a result the competition is

keen, with bids for government contracts often differing by

as little as 0.25%.

a. EXAMPLE: GovzAme.yLt P^ociviejmyit

The GSA procures more than 2 million gallons of paint per

year for the civilian agencies and about half the military

requirements. It can be assumed that procurements by

state and local governments and the remainder of the military

procurements would amount to an additional 3 million gallons.

In the case referred to in L.2.3, a 1% difference in reflectance amounts to a 5 cent per gallon difference in production

costs, and a similar amount applies to colored paints and

other finishes. Because of the highly competitive nature

of the paint industry, production will move toward the low

end of the uncertainty. Therefore, reducing the present

.5% uncertainty level to 0.1% amounts to an increased value

received by the taxpayers which can be calculated as follows:

Reflectance delivered with improved

measurements 85.9%

- Reflectance presently delivered . . . . 85.5%

= Reflectance increase with improved

measurements 0.4%

At $.05 per gallon per percent increase

in reflectance, the increased value

per gallon with improved measurements . $.02

X Number of gallons purchased by

government annually 5 x 10^

= Annual savings $100,000

30
c-3

However, it would be unrealistic to assume that this saving

would actually result, since the increased cost in making

the paint would simply result in higher prices for the paint.

The real advantage to be gained is that the market could be

made more orderly, thereby saving time such as that spent

by GSA and Norris (L.2.3). As it now stands, the specifications are 86 ±0.5%. Since this range of uncertainty is

economically significant, the manufacturers will try to

make the low side of the range, but since measurement

techniques are good only to the same uncertainty they will

quite often miss the mark, even when an honest attempt is

made to hit the middle of the range. Ideally, for a market

of this type to be orderly, three conditions must be met

simultaneously:

1. The range of uncertainty in the specifications

should be no less than really needed based upon

the use to which the material is to be put.

2. The range of uncertainty in the measurements

should be economically insignificant.

3. The range of uncertainty in the measurements

should be at least two or three times less than

the range of uncertainty in the specifications.

Thus, in the present example if the specifications were kept

at the present 86 ±0.5% for paint reflectance but the

reflectance measurements were improved to ±0.1%, reputable

manufacturers would find it more economical to keep the

reflectance around 85.6% than to try to control the

production to bring it even closer to 85.5%. The savings

in wasted manpower in arguments and occasional litigation

over failure to meet specifications could be 10 man-years

among the many paint companies and governmental units

Average salary per year of technologists . . . $10,000

X Number of man-years saved annually 10

Annual saving through elimination

of non-productive labor (R.3) $100,000

b. E)(M{PLE: AiUtomcuUon

Automatic mixing and shading in paint manufacture, which

could be made possible with adequate accuracy in spectrophotometric

sensing, could perform 20% of the monotonous and dirty labor

in paint production for 1/4 the cost. (Assume that only the

eight largest companies automate extensively.)

31
1 c-4

Annual paint production worker payroll , . , .$225 million

X Fraction in eight large companies 0.3

X Fraction of work which could be done by

automation , 0.2

X Fraction by which cost is reduced by

automation 0.75

= Annual increase in productivity (R.3) $10 million

c. EXAMPLE; Jmp^ov^d Uyii^onjfruXy ol V^oducJU-on

Since present procedures cannot be completely relied upon to

produce a uniform product within visual acceptability limits,

in the better paints efforts must be made to keep up with

paints by lot. This effort costs roughly 200 man years

throughout the country by paint warehouses, hardware stores, etc.

numbering lots , keeping up with lot numbers when stocking

shelves, and solving consumer problems arising out of differences between lots. Also by conservative estimates one quart per 100 gallons of paint is wasted in repainting to

the edge of walls, pouring paint from container to container,

repainting an entire panel to cover a single blemish, etc.,

because the control of the appearance is not yet quite

adequate. Also, if an average of 7 minutes per 100 gallons

is spent by painters avoiding mismatches , a million man-hours

will be lost in this way alone. A solid improvement which

would reduce the uncertainties by a factor of five in

practical spectrophotometric measurements for use in the

paint industry could reduce the difficulties from mismatching

by more than half, industry-wide.

Number of man years lost in accounting

for stock by lot each year 200

X Cost per man year $8,000

+

Total value of paint production $3 billion

X Fraction wasted at rate of 1 quart per

100 gallons 0.0025

+

Number of man hours lost by painters

per gallon of paint . . . .- 0.0012

X Average value per hour of time spent by

persons doing the painting $3

X Total number of gallons produced

annually 1 billion

= Annual increase in productivity (R.3). . . .$12.7 million
c-5

R.2.2 EXATLfS FROM THE TDCriLE AND APPAREL INDUSTRY

NOTES I the textile industry, 7000 U.S. companies produce each year

shipments valued at $20 billion. Unlike the paint industry, where

shipping costs from abroad are prohibitive, the textile industry

faces very strong competition from imports. In spite of the very

favorable supply of raw materials for textiles in the U.S., our present import of textiles exceeds the output by $400 million

and the deficit is growing at the rate of $50 million per year.

One of the chief reasons for the clothing industry's favoring

imported goods is higher quality in terms of freedom from flaws

and uniformity of the product. Competing textile manufacturers

abroad have been able to take advantage of inexpensive labor to

perform more detailed inspections than could be afforded in this

country. The United States' clothing industry itself, which

grosses approximately $20 billion per year with $10 billion per

year in value added, is suffering even more than the textile

industry from competition from abroad, with a trade deficit

which has been doubling every four years and currently stands

at nearly $1 billion. Although various import quotas have

been applied to textiles and clothing, these are at the best

stopgap and can be beneficial only if they are used to buy

time for improvement of the domestic industry. The only productive answer to this problem is automation (J) , in which appearance

measurements play a large part. Through proper automated control

and inspection of fabrics, they can be made uniform enough to

allow many cutting and preassembly tasks in clothing production to

be automated as well.

a. EXAMVLE: Inipzdtlon o{i MatoAlal BzioKo. Mana{tacX.uA Clothing

Manufacturers of better quality clothing inspect much of the

material going into their products. An inspector can visually

inspect about 10 yards per minute at most, and there is some doubt that he sees very much after an hour on the job. Since

10% of the fabric used is inspected this way, the cost of this

inspection along is $3 million per year, of which 95% could be

saved by automated pre-inspection. However, if automated preinspection were to become more widespread an even greater

advantage could be realized. Approximately 0.1% of the garments

produced contain flaws which on the average represent a real loss

of 20% per garment for anything from extra handling in special

sale to discarding. This savings can only be realized, however,

if this type of inspection is accurate. By definition, a flaw

can be seen. If an inspecting machine "sees" four times as many

flaws as those which the human observer would consider important,

the saving could be wiped out in wasted materials. Therefore, a standard method for determining the sensitivity level to set the

instrument, a problem in appearance evaluation (I), and a means

of judging instrument performance, a problem in time-varying spectrophotometry, will both need to be solved before this type of

33
inspection will be accepted. Solving this type of problem

would be most efficiently done by NBS, since it would be

a natural part of solving many similar problems. The value of

solving this problem could be calculated as follows:

Total annual value added in the

clothing industry ... $10 billion

X Fraction of this in mass produced

clothing 0.6

X Fraction of mass produced clothing

affected by flaws in textiles 0.001

X Fraction of trade which could benefit from

automated inspection 0.5

X Fraction of value added which is lost

due to flaws 0.2

= Annual waste in value added which is lost

could be avoided through automated

pre-inspection $600,000

EXMPLE: Inabltlty to Communlcatz Colon, and ApptoAance.

The color and appearance aspects of the textile market offer

an excellent example of a disorderly market . In one manufacturer 's knitted sportswear operations, 35% to 40% of the

fabric received is rejected because of improper color.

This material is not wasted, of course, since it can be

resold, but the shipping, handling and half the inspection

costs must be considered a total loss. These problems

exist in a market where for the most part an honest effort

is being made to communicate specifications and meet them.

The estimated total value of production of this type of

material is $2 billion per year. Shipping out, handling,

inspecting, shipping back, handling again and reselling

will add about 10% to the cost of the material receiving

this type of treatment , which would be over 10% of the

production. If absolute specifications and accurate measurements could be made, most of these difficulties could be

eliminated for an estimated increase in productivity of over

$20 million per year in this small segment of the industray

alone. There is little doubt that if the three criteria

for an orderly market (R.2.1a) could be met in this case through improved appearance abstractions (I) and spectrophotometric measurements, there could easily be an industrywide savings of time, handling, and confusion between textile

distributer and clothing manufacturer, the value of which

can be calculated as follows;

34
c-7

Total value of textiles

Total value of annual

textile production . $20 billion

X Fraction of this used in

manufacture of colored clothes 0.25

X Fraction of this rejected because

of poor color control 0.05

X Fraction added to cost by

rehandling 0.1

= Annual wasted effort which could

be avoided through an orderly

market $25 million

c. EXMPLE: Advantagz oj^ ?A.oduct Sp^ci^A^ccutiovL and JmpdcZlon

One of the principal advantages offered by import fabrics over domestic fabrics as far as the domestic clothing industry is

concerned is that many of the imports guarantee flaw-free

fabrics and better repeatability in appearance. U.S. industry

cannot compete at this level if inspection and sorting is done

by manyal labor. However, industry has in many cases been

"burned" by failures of the early appearance instrumentation

to live up to claims, and therefore regards such instrumentation

with suspicion. Activity by the National Bureau of Standards

in producing accurate, reliable, and practical measurement

procedures would help dispel this reluctance to automate.

Automatic inspection for flaws and classification by lot in

appearance would enable the domestic manufacturers to compete

on an even footing with the best import competition, and the

deficit in import could be cut at least in half in a pH.oddX.cXi.V(L manner.

Annual trade deficit in textiles . . . $400 million

X Fraction of trade which could be

regained by improved U.S. goods . .0.5

= Improvement in balance of trade . . . $200 million

d. EXAMPLE: Advantage, TmpaAce.ptible. ViiioAmco^

The color control problem described in part b of this section

is brought about by the clothing manufacturer's attempt to

produce garments which could be hung side by side on the same rack for sale. Even more care must be taken, with special

marking procedures for cutting and assembling garments, to make

sure that the material matches at seams, where very little

difference can be tolerated. The type of technological

35
c-8

advancement being considered in the ETIP proposal (J)

Is one by which fabrics would be produced to very high

tolerances through automated controls. If such fabric

production could be attained, marking and the associated

handling could be eliminated and much sub-assembly work

in garment production could be done automatically. This

automation could easily reduce the value-added cost of

U.S. clothing production by 20% in areas directly affected

and would place our textiles at an advantage in the world

markets as well. The benefits of success in such an undertaking could mean a reduction of the clothing

deficit in the balance of trade by one-half. The over-all

savings could be calculated as follows:

Annual trade deficit in clothing .... $1 billion

X Fraction by which cheaper U.S.

garments could reduce the deficit +

Annual value added in clothing

industry

X Fraction of industry which could

benefit from automation 0.25

X Reduction in costs through automation. 0.2

= Annual savings from combined

textile and clothing production

automation $1 billion

(Discussions with Mr. Doug Marchio and Mrs. Georgi Egan

of Levi-Strauss, San Francisco, California are gratefully

acknowledged.

)

R.2.3 EXAfiPLES FROM feiCINE

NOTES I The field of medicine is difficult to describe simply in terms

of value of products, since much of what is involved is services.

Therefore, for purposes of this discussion, the annual value of

direct medical services will be set at $35 billion, the sum of

direct payments by individuals for medical care, insurance benefits

for medical care, and government subsidy of medical care. (The

latter is a small part of the total.) Of this amount, it is

probably reasonable to assume that five percent, which is $1.7

billion, goes for clinical tests. An additional approximately

$2 billion, mostly in government funds, is spent annually on medical research. There are no figures available to connect

suffering, disability, or death to improper diagnosis resulting

from inaccurate laboratory tests. However, percentage values

given to indicate an increase in the useful results of the

tests would be presumed to apply as well to a reduction of these

ill effects.

. 0.5

. $10 billion

36
c-9

a. EXAMPLE: Ctiyiical TOyiti - ?n.2A(int TzchviiqaQA

As mentioned in part 5.2, clinical tests are complex analyses

performed on complex substances. In the present technology,

although 90% of the clinical tests are evaluated in the final

analysis through spectrophotometric measurements, the error in

the spectrophotometry is a small part of the total error in many

cases. Most current tests are regarded as fairly satisfactory,

but there are difficulties in analyzing blood and urine of

comatose patients, where often there are no clues as to the cause of the trouble. Tests for the presence of drugs often

do not give correct results, and hormonal analyses regularly

give wrong answers. Improvement of the type of spectrophotometric measurement routinely used could easily add one percent to the value of such tests overall in terms of

improved determinations, but probably not much more. Proper

publicizing of the approximate accuracy of the measurements

under the conditions of the tests would add another two percent

to the value of the tests by dispelling false confidence. Both

contributions depend on the type of thorough knowledge of the

measurement process which is the goal of the proposed spectrophotometry program. In terms of value received for present

type clinical tests, the savings could be calculated as follows:

Annual cost of clinical tests $1.7 billion

X Fraction of tests involving

spectrophotometry 0.9

X Fraction of value gained by

improving spectrophotometry 0.01 + Fraction of value gained by

better understanding of limitations . . 0.02

= Annual increased value of present

clinical tests $46 million

b. EXAMPLE; MzcLLcjot R^AOMAck IMlng PA.^4e^^t Ttckyilque^

Medical research in which clinical analysis is a tool undoubtedly

suffers more from poor test results than general clinical

practice. If more uniform data could be gathered from the results

of general clinical practice, this would be extremely useful.

Even more important is a thorough understanding of the magnitude

of the uncertainties in the measurements and the propagation of error in the data analysis (5.2,E). There is evidence to indicate

that misunderstanding of the accuracy of spectrophotometric measurements and the reliability of corresponding correlations is quite common among medical researchers. Improving present spectrophotometric techniques and providing literature by which data analysis

would be done more realistically would increase the effectiveness

of medical research overall by two percent for the following annual

increase in value of research:

37
I

I C-10

Annual expenditure on medical research . , . $2 billion

X Fraction of increase in value due

directly to improved spectrophotometry ... 0.01 + Fraction of increase in value due to

better data from field labs 0.01

= Annual increase in the value of research . . $40 million

c. EXAMVLE: him AppH-oncke^ to CLiyilcaZ SpzcJxophotomntfiy

In current procedures, the spectrophotometric measurement system

as an indicator for the final stage of a series of chemical tests.

Usually measurements are made at only one or two wavelengths in

a particular test in order to evaluate the presence and quantity

of one particular substance. However, much more is within the

power of present technology. It is quite possible to measure

and record an entire spectrophotometric "fingerprint" of a substance such as blood or urine, including photoluminescent data

for many levels of excitation. Such data, taken at regular intervals as an individual receives medical checkups, could serve to

indicate changes and point to further tests which could be made.

There is every reason to believe that such a procedure could be

done on a practical scale with instruments not much more complicated

than closed circuit television, and that, properly standardized,

such survey differential analysis based on individual records could

make clinical testing 25% more effective for an increased value

which can be determined as:

Annual cost of clinical tests $2 billion

X Fraction which could be eliminated

by a good survey procedure 0.5

- Fraction which survey procedure would

add to present tests 0.25

= Annual savings in clinical tests $500 million

(Discussions with Dr. Robert McCullough, heat pathologist of Holy

Cross Hospital, and Dr. David Goldenberg, practicing physician.

Silver Spring, Maryland, are gratefully acknowledged.)

AN EXWLE FROM RMTE Sem

NOTES! Ill a report to the House Committee on Science and Astronautics

(C.3.95), the potential net benefits over a twenty year period

of a program for remote sensing of earth resources was indicated

to be in excess of $3 billion per year. Unfortunately, the

gross value of the program is not available, but from the description of the technology it is estimated that the program

38
C-11

would be at least as expensive as the present space exploration

program, or approximately $4 billion annually. Therefore,

benefits from the program will gross $7 billion.

a. EXAMPLE:

Conservatively, half of the measurements will be done at wavelengths in the range of spectrophotometry as herein defined (2),

and of these, half will depend upon spectrophotometric calibrations totally or in part. This means about $2 billion worth

of the annual results depend upon accurate spectrophotometry.

If standardization at the present level is used, three-fourths

of the value of this portion of the data is lost. If the best

current techniques are applied, this loss could be reduced to

one-fourth. With applications of the improvements in spectrophotometric measurements, particularly in reflectance, as proposed herein, it is quite probable that the measurements

could be made as effective as described in the Thiel and Graves

report (C.3.95), thereby resulting in an increased value which

can be calculated as follows:

Average annual benefits estimated for

remote sensing program $7 billion

X Fraction of measurements in spectrophotometric wavelength range (2) 0.25

X Fraction of measurements depending

upon spectrophotometric calibration . . . 0.25

X Fraction which cannot be calibrated

unless spectrophotometry is improved. . . 0.25

= Annual loss if spectrophotometry

is not improved $109 million

R.2.5 AN EXWLE FROM CONSERVATION

NOTES I Copper is valuable and in short supply. As a result, approximately half of the copper produced in the United States is

recovered from scrap. The production of copper alloys, such as bronze and brass, is over 90% from scrap. The present value of

brass produced from scrap is in the neighborhood of $250 million

annually (C.3.96).

a. EXAMPLE:

In order for high quality brass to be made from scrap, the

various types of brass must be separated. The highly trained

labor for this task is vanishing (5.4.3), so that either the

quality of sorting will drop or the price of the labor will

rise, more likely the former. The result will be a net loss

in productivity or value of product of about 10%. There is reason to believe that sufficiently sophisticated data

39
C-12

analysis (7.2.3) can be incorporated into a very specialized

and inexpensive instrument to recognize scrap "shovm" to it.

Therefore, for about 1% additional cost for instrumentation,

unskilled sorters can be employed to do the same job, providing

employment for unskilled labor and maintaining productivity.

The value of this can be calculated as follows:

Annual value of brass made from

scrap $250 million

X Fraction which would be lost under

unskilled labor without instruments . . 0.1

- Fraction of cost to buy sorting

instrumentation 0.01

= Annual net value retained through

instrumentation $23 million

R.2.6 AN EXAiiPLE FROfi AGRICULTURE

NOTES! The United States produces about 30% of the wheat for export in

the world. This market amounts to $1 billion annually.

a. EXAMPLE;

The other large exporters of wheat are sorting their crops

by food value through the use of chemical tests performed

by military and other governmental personnel. Spectrophotometric methods would make it possible for the U.S. to

perform such inspections without making use of government

labor at a competitive cost. If such sorting enables us

to increase our market by as little as one percent, the

improvement in our balance of payments would be:

Annual favorable balance of trade ... $1 billion

X Possible improvement through

sorting by food value 0.01

Cost of instrumentation $1 million

= Annual increase in favorable

balance of trade $9 million

R.2.7 AN EXATPLE FROM RESEARCH AND INSTRUMBfTATION

NOTES! The current market for spectrophotometers (C.3.1) in the United

States is $100 million. Although the net export of U.S.

scientific instruments is about 10% of our total production,

analytic instruments face much stronger competition from

abroad. A rough estimate would be that 60% of our analytic

spectrophotometers are domestic and 40% come from abroad,

40
C-13

and that the trend in the recent past has been for an increase

in imports and a corresponding decrease in exports.

Increased confidence in domestic instruments which would follow

from improvements in performance and status brought about by a better measurement system and the backing of an effective national

laboratory could bring 10% of the U.S. market back to domestic

instruments and also increase our exports of analytic instruments

by 10% of our present production. The value of this can be

calculated as follows:

Annual market in U.S. for

spectrophotometers $100 million

X Fraction brought back to U.S.

instrument companies 0.1

+ Fraction being produced currently

in U.S 0.6

X Fraction of this for increased

exports 0.1

= Annual increase in favorable

balance of trade $16 million

The examples for specific cases above add up to a R.3 TOTAL SAVINGS of approximately $2 billion per year. There are, of

course, many other possible savings, but most of them would be relatively

small. These savings take the form of increased productivity through

automation and an improved balance of trade. A decrease in employment through

automation is not regarded as a detriment, since this represents increased

productivity which, through redistribution of labor, should result in

shorter working hours and increased leisure time, both of which are generally regarded favorably.

Care must be taken in drawing

Ri4 COMCLUSIOfJS from analyses such as those obove. The total savings

indicated above are in reality pot(LV\XAjoJi savings which depend upon many

other factors besides improved spectrophotometric measurements. For every

hour of effort by IBS to improve spectrophotometry, hundreds of hours

of engineering and development will be required to take advantage of the

improvements. However, none of these benefits can be realized without

the improved measurements. In addition, a stable measurements system,

backed by a national laboratory which can provide all-important verification of accuracy and assistance with improvements, has a catalytic

effect, stimulating exploration and investment which might otherwise be

discouraged. An effective program in spectrophotometry at IBS can provide

an excellent return for the funds (P) invested in it.

41
D-1

APPENDIX D. FACTORS AFFECTING ACCURACY IN SPECTROPHOTOMETRIC

MEASUREMENTS

The following are two appendices, E and H from the 1972 report of the

spectrophotometry study by the IBS group. They are included here to illustrate the difficulties which can be encountered in making accurate spectrophotometric measurements and the way in which good standards can make the

measurements both easier and more accurate.

42
D-2

Appendix E (From 1972 Report)

Accuracy in Spectrophotometry

Spectrophotometric standardization is probably best described as elusive,

this elusiveness being revealed in the extreme care required to define what is

to be measured and to make sure something else is not measured instead. An

understanding of just what is involved in the concept "accurate spectrophotometric measurement" is essential to the full understanding of the need for a national standards laboratory to have an active program in spectrophotometry.

Certain errors, principally those from processes governed by chance such

as the emission of photons and electronic noise, are random in nature. In

principle, these can be reduced by means such as using stronger sources of

radiation and measuring over longer periods of time. In practice, a point

is usually reached at which the advantage to be gained by further reduction

of this random error or imprecision is not worth the additional effort. At

this point, by statistical analyses of the data from a number of similar

measurements, one can assign a range of statistical uncertainty which is

called the "precision" of the measurement. With modern instrumentation, the

precision of transmittance and specular reflectance measurements is typically

on the order of ±10"^ on a scale in which 1 represents a clear path or perfect

reflector. Measurements of bi-directional reflectance of diffuse reflectors

are generally precise to about ±10 ^, where 1 is the reflectance of a perfectly

reflecting diffuser under the same geometry. The precision figure gives a practical lower limit for the uncertainty in the measurements.

In spectrophotometry, far larger errors regularly result from systematic

or non-random causes. It is these errors which result in poor technological

communication, hampering scientific achievement and causing disputes in commerce,

and it is to reducing these systematic errors that a standards laboratory should

address itself. A few of the sources of such errors will be presented here in

order to illustrate the types of difficulty which are encountered and indicate

the magnitude of the error which can result from some of them. There have

been numerous attempts to separate these sources of error into categories, as for example into "sample errors" and "instrument errors" (C.3.48). Such

separations are artificial and not generally successful. The measurements

must be considered as a whole—an interaction of experimenter, instrument and

sample—if a basic understanding of errors is to be had. Therefore, although

the sources of error are presented in groups of loosely related errors and

numbered sequentially, the various sources of errors and groupings can be

interrelated and often are.

One source of error is non-linearity in the detection system, i.e., the

spectrophotometer output is not simply proportional to the radiation flux being

measured. This may be due to

Ell iO'^-LINEAR ELECTRONICS^ either signal amplifiers or servo-systems, or it

may be due to photodetector non-linearity resulting from

Ei2 SPACE CHARGE EFFECTS the photocathode of vacuum photodetectors

E.3 DETECTOR SATURATIQl or Ei^ DETECTOR FATIGUE^ which is particularly noticeable in photomultiplier

tubes. The fatiguing effects can make the results depend upon the time between

43
D-3

measurements and the duration of the measurements in an unpredictable way.

The effects of space charge or saturation are more predictable, with care can

be held to approximately 10"*^ of the maximum signal, and are correctable

(C.3.25). Other factors which affect the performance of the detection system

include

E.5 FLUCTUATIONS IN LINE VOLTAGE and

E.6 MAGNETIC FIELD FLUCTUATIONS. Although the presence of a constant or a steady state alternating magnetic field will not usually affect the performance

of a detector system adversely, performance will be degraded by changes in

magnetic field, particularly at the detector, during the course of a measurement.

Such changes can occur when nearby electrical equipment, particularly high

current DC equipment, is switched on or off, or when large pieces of ferromagnetic materials or permanent magnets nearby are moved. Changes due to these

causes can be as high as 10 ^ of the detector output at the time.

A source of non-linearity which occurs in reflectance measurements when

an integrating sphere is used to provide hemispherical illumination or viewing

might reasonably be called a

El 7 SPHERE EFFICIENCY error (C.3.9). This error comes about because the sample

being measured is also part of the sphere wall, thus introducing the reflectance

of the sample into the measurement both directly and as a factor in the efficiency

of the sphere. This effect is greatest in single beam instruments where deviations

of up to 10% of the measured reflectance can be expected. As long as the

reflectance of the sample does not change significantly within the bandwidth

of the instrument, this error is negligibly small in a double-beam spectrophotometer,

however, in broadband double beam instruments such as tristimulus colorimeters

and instruments measuring luminous or total reflectance, errors of several percent of the instrument output can occur.

El 8 LEAKED RADIATIOfJ which enters the detector via the wrong route or from a separate source of radiation is particularly troublesome when unmodulated

radiation is used in the measurements.

E.9 RADIATION OF OTHER WAVELENGTHS than in the band desired, whether leaked

in or passed by the monochromator system, as with other orders or ghosts in

a grating instrument, can be particularly troublesome when measurements are being made in strong but narrow absorption lines. Another type of stray light

error, referred to as EilO BLACK SATLE ERROR^ occurs in integrating sphere instruments. Light

scattered from the beam forms a diverging halo around the main portion of the

beam. Much of this halo falls outside the port area on the sphere, causing

reflectance readings even with ideal non-reflecting samples (black cavities).

Even on high quality instruments these readings can be as high as 5 x 10"^ of

those from the ideal diffuse reflector (C.3.49).

The foregoing errors are more closely related to the instrument than to

the sample. As the interrelation of instrument and sample are taken into account, more possible sources of error arise.

Most definitions of spectrophotometric measurements assume the absence of

E.n POL'\RIZATia\| OF IlCIDEiT RADIATION and the absence of

Ei]2 POLARIZATION OF DETECTOR SB'NSITIVITYi Errors win be introduced in

measuring specular reflectance and the transmittance of birefringent or dichroic

44
D-4

materials, since these are dependent upon the polarization of the incident

radiation or affect the polarization of the radiation which leaves the sample

(C.3.50). Several other sources of error are related to the nonuniformity

of photodetector sensitivity across the sensing surface. Not only is the

sensitivity usually a strong function of position on the surface, but this

function may also change with wavelength. Therefore it becomes important

that the same portion of the photodetector surface be used at all times.

Even when this effect has been effectively neutralized by using an integrating

sphere, the presence of stops in the light path from the sample to the

receiver may cause changes in the size and position of the flux of radiation

from the sample to be important. In transmittance measurements, such changes

can result from an image shift due to a E.13 TILTED SAMPLE or E.l^ fO-PARALLEL SAfiPLE FACES, or a change in focus due to

E.15 CURVED SAfPLE FACES or simpiy the

E.16 CHANGE IN OPTICAL PATH LENGTH due to introducing material of a different

index of refraction into the beam. These effects can introduce errors of 10 ^ or more if not carefully handled. In addition to defocusing aaused by introducing a sample of a given index of refraction into a beam,

E.17 liJTERREFLECTIOfjS between the sample faces and other parts of the

instrument can introduce stray light errors, and

E1I8 MULTIPLE REFLECriOflS between faces of the sample can produce additional

images, each with its own problem of focus. This latter effect can be on the

order of 2 x 10"^ of the incident flux for nearly transparent samples.

An intrinsic difference in measurements between instruments having different amounts of convergence in the beam, a

El 19 PATH I FfJfiTH ERROR, ^^.n be introduced even in gage measurements. Data

from the instruments cannot be simply reconciled because of the exponential

dependence of attenuation upon path length, but in obtaining the ratio of

the transmittance of one filter to that of another with transmittance a factor of 10 less a difference of approximately one half percent will be

encountered when using a collimated beam instrument as compared to an f8

instrument. Such an error can accumulate to several percent in calibrating

very high density filters or measuring strong absorptions. Because of the

E.20 UflEX OF REFRACTION CHANGES giving rise to the anomalous dispersion

phenomena near absorption lines, the measurement of absorption bands or lines

to determine chemical concentration may be very strongly influenced by the

factors listed in E.13 through E.19.

Other optical phenomena which must be accounted for in order to insure

accurate measurement are

El 21 DIFFRACTIOf^J. which is particularly troublesome in dealing with attenuating

screens (L.2.2) and

Ei22 SCATTERIfjG ^y macroscopic granular discontinuities in a substance.

If scattering is introduced unintentionally, or in any case in which the

scattered radiation is not the quantity of interest, then its contribution

45
D-5

to the measured flux must be determined and corrections made. Even when

scattering is the phenomenon of interest, as in the measurement of haze, total

transmittance of translucent materials, and diffuse reflectance, scattering

introduces several other possible sources of error. One of the most difficult

problems arises because of the

E,23 DIFFdSIQN OF RADIATION within the sample. In theoretical treatment of

scattering media this phenomena is taken into account in only one direction,

that normal to the surface of a uniform and uniformly illuminated infinite

slab of material. A unique definition can be properly formulated in this

way, but actual measurements are made with light beams, which are of finite

cross section, so proper account must be taken of diffusion parallel to the

surface of the sample as well. This is commonly done by illuminating a small area of the sample and observing a large area or vice versa. A one percent error in measuring the luminous reflectance of white paint has been traced

to improper handling of diffusion (L.2.3) and there is reason to believe that

substantial errors may result from the use of NBS calibrated vitrolite gages

(N.2.2) for the same reason. Not only is the total reflectance affected,

but errors in measured chromaticity also result from diffusion, since the

extent of diffusion and hence diffusion losses will be greater at the wavelengths at which less absorption occurs. The effect of diffusion losses on color measurements is a trend in the direction which can be roughly described

in the Munsell system as a decrease in both value and chroma, or on the CIE

chromaticity diagram as a shift toward the source point. Developing proper

measurement techniques to account for diffusion within the material, a difficult

task for even the relatively opaque ceramic materials, is becoming extremely

important with the increased use of highly translucent plastics (L.2.9).

In measuring the properties of scattering materials, it will also be necessary

to properly determine the effects due to

El 2^ SA'^'PLE THICKFiESS ^^'^ the contribution to reflectance measurements of the

E.25 REFLECT«E OF THE SAFPLE BACKING material (c.3.51).

Effects similar to diffusion occur in materials which fluoresce

because of

E.26 IffTERNAL ABSORPTION m RE-B1ISSI0N OF FLUORESCENCE RADIATION are even

more difficult to treat. This effect is particularly strong near resonance

lines. Failure to deal with this effect carefully is one of the reasons that

estimates of uncertainty in fluorescence measurements are as high as 25 percent

for strongly fluorescing materials (C.1.17). Including

E.27 UNRECOGNIZED FLUORESCE'IT RADIATION in a measurement of a property

unrelated to fluorescence is a potential source of rather large errors.

If a very strong flux of radiation, such as that from a laser, is used

to illuminate the sample, non-linear phenomena such as E.28 SATURATION OF ABSORPTION LB/ELS.

E.29 IffUCED ABSORPTION, and

El 30 INDUCED RE~EI1ISSIQ^ TMay occur, and must be properly taken into account.

Ei31 HEATING OF THE SAflPLE ^an also occur as a result, producing a change in

its properties.

46
D-6

In the case of gage measurement (H) , the gages themselves can be a source of error. The usual difficulties which come to mind are E.32 ERRORS IN GAGE CALIBRATIOij and either temporary or permanent

E.33 INSTABILITY OF GAGE MATERIALS. However an equally important source

of error in gage measurements which can embrace any or all of the other sources

listed here is the

E.3^ IITROPER USE OF GAGES^ i-e. using them for purposes other than that for

which they are designated.

Another group of potential source of error is linked to the definition

of the wavelengths involved in the measurements. An

E.35 INCORRECT WAVELENGTH CALIBRATION can obviously result in errors. Errors

can also be introduced by the

E.36 EFECTS OF FINITE BATOIDTH. which are particularly noticeable in

measurements in which the spectrophotometric properties undergo their principal

changes within a spectral range which is within an order of magnitude of the

instrument bandwidth. More rapid fluctuations tend to be properly averaged

over the bandwidth as do less rapid fluctuations. In all measurements involving

a finite bandwidth, but particularly in the broad band measurements used in

colorimetry and photometry, accurate control of the

El 37 RELATIVE SPECTRAL WEIGHTING of the source intensity - system transmittance - detector sensitivity combination is necessary in order that the measurement defined

will actually be the one performed (see also E.7).

Finally, a very important source of error is improper

E.38 SPECIFICATim OF SPECTROPHOTOflETRIC f€ASURBEITS. aii of the foregoing

discussion of errors in spectrophotometric measurements contains the implicit

assumption that the measurements will be well-defined. Although it appears

almost tautological to note that inaccuracy can be defined only after accuracy

has been defined, it is quite probable that half of the difficulties in spectrophotometry arise from poor definition.

In order to amplify the foregoing assertions, an idealized step by step

procedure for defining a measurement will be given. For practical or historical reasons, measurement procedures are seldom arrived at in such an orderly manner. Nevertheless, in order or not, all of the steps in the

procedure should eventually be carried out to produce a useful, well-defined

spectrophotometric measurement.

The first two steps, which are closely related, are to

E.38.1 SPECIFY PRECISELY THE PROPERTY WHICH IS TO E DEER1INED and to

E.38.2 DETERfllE CORRELATIONS BETICEN TT^AT PROPERTY A[€ RELATED SPECTROPHOTOfCTRIC

FEASUREriEfITS I should be emphasized that the property to be determined is

usually not spectrophotometric and often not even optical. Examples of such

properties are the rate of emission of fly ash from a smokestack or exhaust

(Q.8), the composition of scrap material being reclaimed (5.4.3), the size

of holes etched in a TV tube mask (L.2.2), the thickness of plastic films,

and the concentration of nutrients in sea water (C.1.51). The definition

of the property should be as precise as it can be made and should include the

47
size errors which can be tolerated in the determination. It is important

that these errors be estimated as well as possible, since the tolerences

being too tight might exclude attractive alternative measurement schemes from

consideration, while their being too loose might result in the adoption of

spectrophotometric measurements which could never yield adequate data to

provide the accuracy which would eventually be found necessary. Once the

first two steps have been carried out, one should then carefully

E.38.3 EVALUAIE 1HE PRACTICALIIY OF ALTERfJATIVE flEASURBE^TS. This evaluation

should look both ways, ahead to the conditions under which the measurement

will be used in the "field" and back, through the correlations to the property

which is to be measured. If the measurements are to be made out of doors by

semi-skilled workers on a highway crew, for example, a scheme with poorer

correlation may be chosen if the corresponding instrumentation can be made

more rugged and easier to use. On the other hand, if the end use will occur

in a research laboratory, the best correlation may be sought with little

regard for the delicacy or complexity of the instruments.

Although these three initial steps appear obvious, the first two are often slighted. An example of this can be seen in the discussions of the pros

and cons of narrow wavelength band versus broad wavelength band measurements

of absorption in chemical work. Much of the controversy could be resolved

by carefully defining the property which is to be evaluated. One may wish to

determine the rate at which molecules are excited to a given state in order

to study rates of photo-chemical reaction, or one may simply wish to determine

the concentration of a particular solute in a solution. In the first case,

the absorption of light, which is truly an optical property, is for all practical

purposes the property of interest, and this correlates in a one-to-one fashion

with the total absorption in the line or band of interest. Therefore, from

the standpoint of correlation, one would use a broad band instrument or one which scanned the absorption lines to evaluate this property. Narrow-band

measurements at the absorption peak would have to be supplemented by other

experiments in order to obtain the same results, since the correlation is not

as direct. In the second case, the property of interest is the concentration,

which is not an optical property at all. In this case, since the absorption

coefficient in different parts of the band, the simpler linear relationships

between concentration and the spectrophotometric data known as Beer's law

will occur only when the instrument bandwidth is very narrow compared to the

absorption bandwidth (C.3.52). (This problem is mathematically related to

the path length problem indicated in E.19). Therefore which bandwidth is used

or what corrections are made for data obtained with an intermediate bandwidth

will depend upon the property which is of interest. Unfortunately concepts

such as these, which should be generally and easily understood, are confused

in the literature with fuzzy rhetoric couched in poorly defined and often

argumentative sounding terms such as "true absorbance".

The next step, once the spectrophotometric measurement to be used has

been chosen, is to

E.38.i| DEVELOP m "EST THE MEASUREEffT PROCEDURE. This would mciude

determining whether gages should be used, and, if so, what gages. This step

is almost universally regarded as important and is usually well done except

for testing for the contributions of systematic errors and including corrections

48
D-8

for these or means for avoiding them. This is generally either because those

developing the measurements have been unaware of the magnitude of the errors which can be introduced by some sources or have not had instrumentation available

to properly evaluate them. In this part of the development, the expertise

and supplementary measurements which can be supplied by a well-equipped

national laboratory can be extremely valuable.

When the measurement procedure has been developed and tested adequately,

the next step should be to

E.38.5 THOROUGHLY DOCUFEiT THE DEVELORefT OF THE ftASURBiB^T. such documentation

should include a complete and orderly summary of all of the work done under the

preceding steps. It should include the complete definition of the property to

be determined, alternative measurements considered, the reasons for rejecting

the alternatives, the reasons for choosing the method used, the tests made in

developing the procedure and summaries of the results, what possible sources of error were evaluated and how, what possible sources of error were not evaluated

and why not, what gages are required and what properties of these are important,

etc. This documentation should generally remain with the laboratory or group

responsible for the measurement and should be open ended to allow for future

testing or modifications of the procedure. This type of documentation is essential

for standardizing organizations such as ANSI, ASTM, and NBS. It is also

advisable in a somewhat less strenuous form for individual laboratories or industries developing their own measurements, since in almost every case the

savings realized by being aware of potential pitfalls and avoiding repeated

evaluation of sources of error will more then offset the cost in time spent on documentation. The information contained in complete documentation of this

type is the only basis from which the accuracy of measurements made using the

procedure can be evaluated. To the extent that the uncertainty in the definition

of the measurement process affects the results of the measurement, it must be

regarded as another source of error. Despite these considerations, careful

documentation is rarely done (N.l).

Finally, if the measurement is to be performed by anyone other than those

who develop the method, it is highly advisable to

E.38.6 Jmim THE MEASURBEIT FOR PRACTICAL USE. i.e. provide simple

descriptions of the equipment and procedure to be used and, when necessary,

descriptions of the important difficulties which could be encountered. Such

documentation would be a guide for those to whom the results of the measurement

are of much greater interest than the measurement process itself. The standard

procedures published by ASTM and ANSI are examples of such documentation.

All of the preceding discussion has been centered upon how accuracy

is defined and obtained with no disucssion of

E.39 THE NEED FOR ACCURACY, Particular calls for accuracy are mentioned or implied in the main body of this report, particularly in section 5. In general,

the nee-^ for accuracy in spectrophotometry arises in the same way that need

for accuracy arises in any field of measurement. It arises from the need for

specifications to govern commerce; it arises from the need to control the quality

of production from day to day and year to year; it arises from the need to

communicate between buyer and seller, between artist and artisan; between those

who must enforce regulations and those who are attempting to conform to the

regulations, and in general between technical workers of all kinds; and it arises

from the need of scientists and technicians to be able to record the results of

their efforts in such a way that they can be built upon in the future.

49
D-g

Appendix H (From 1972 Report)

Gage 'Measurements

A spectrophotometric gage is a physical object which embodies a spectrophotometric property and which is used as a basis of comparison in

measurements of that property. For example, white ceramic tile which reflects

light diffusely and nearly independently of wavelength is often used as a gage in diffuse reflectance measurements; colored glass can be used as a gage of color measurement of transparent materials; polished black glass is

used as a gage for gloss, etc. Almost all highly accurate measurements in

applied spectrophotometry involve the use of one or more gages, and indeed

most ref lectometers can only make gage measurements. Because of this important role played by gages in spectrophotometric measurements, it is important

that the advantages to be gained and the pitfalls to be encountered in gage

measurement be fully understood by those with strong interest in spectrophotometric measurements.

As an illustration of the

H.l ADVAf'JTAGES OF USING GAGES> consider an example of an instrument which

is assumed to be linear. In this case, the evaluation of a property relative

to the gage property can be expressed by:

S V* = V* ' (Eq. IH)

g

where

is the assigned value of the gage property

S is the instrument output signal when measuring

^ the gage

is the instrument output for the unknown sample and

P* is the value of the property P of the unknown sample as u u determined by the measurement

It is obvious from the form of the equation that as long as the instrument

is linear (Sx = kP^) , other details of the relationship between and P^

need not be known. The

H.1.1 fCASUREreir is calibrated by the gage. THs is by far the most important

advantage of gage measurements , particularly in measurement involving scattering

phenomena such as diffuse reflectance or translucence . Most instruments used

to measure diffuse reflectance are incapable of being calibrated in any other

way than with gages. This advantage is being recognized to the extent that

in many new instruments gage comparisons are built into the measurement and

data reduction procedures, and the operator only receives data after it is

reduced by means of the assigned gage values (C.1.10, C.2.76, C.3.57). The raw readings from the instrument are used only to ascertain that the instrument

is operating with signal levels within acceptable ranges.

50
D-10

A requirement of a good gage is that it resembles the unknown sample

as closely as possible. In applications to production quality control,

a calibrated sample of the product can serve as an excellent gage. Under

these conditions, properly used

H.1.2 (^GES cm REDUCE [EASURHen" ERROR. suppose that m the example

in the preceding paragraph, the instrument response were quadratically

non-linear, i.e.

S = knP (1 + kiP ) X ^ X X

Making a substitution based on this non-linear response in Eq. IH, one obtains

P* = P u u

ki(P - P„)

1 + —-^

1 + kiP

Thus, the error decreases with decreasing difference between the property

and the gage. For example, in measuring a filter of transmittance 0.45 directly

(open transmittance = 1) an instrument might introduce a non-linearity error

of 0.01, whereas in measuring this filter against a gage filter of transmittance

0.5, this nonlinearity error would be reduced to -0.0005. Not only can nonlinearity be reduced, but gages can be used to reduce errors due to other

instrumental causes such as drift and improper spectral and spatial weighting

of instrument sensitivity. In general, there is no question that the proper

application of gages can make measurements simpler and more accurate.

The advantages and the

H.2 DISADVMAGES OF USING GAGES are very closely related. Since measurements

are calibrated by the gages, the use of gages can lead to

H.2.1 PROLIFERATia^ OF ftASURB-E^IT SCALES through the use of many different

gages. An excellent illustration of this occurs in diffuse reflectance

measurements for which in various times and disciplines calcium carbonate

blocks, deposite of magnesium oxide smoke, pressed magnesium oxide powder,

pressed barium sulfate powder and coatings of sodium chloride deposited by

spraying have been used as unity reflectance gages. Obviously, the literature

in the field is quantitatively in a state of confusion. The only way in which

this difficulty can be resolved is for standards organizations to define an ideal scale for each type of measurement and to assist those using gages to measure the gages relative to this ideal scale. (In the case of diffuse

reflectance, for example, a natural basis for the scale is a perfect Lambertian

reflector.) The user, in turn, has an obligation whenever possible to correct

measurement and gage errors toward the ideal when such errors are discovered,

rather than retain his own scale in order to "keep the numbers the same".

Rarely is the continued use of an arbitrary scale justified, and values based

on such scales should never by published deliberately.

In stark contrast to H.1.2,

H.2. 2 GAGES CAfJ INTRODUCE ERRORS. one way in which this can occur, of course,

is through errors in measuring the gage. Another less obvious way is brought

about because the instrument is in some way sensitive to properties other than

that which it is desired to measure. If the gage and the sample being measured

differ with respect to one or more of those properties, an error can be

51
D-11

introduced. A clearcut example of this is presented in (L.2.3). In that case paint was being measured against an opal glass gage which differed in

the way in which light spreads within the material by diffusion. Since

the instrument was sensitive to such spreading, a measurement error resulted.

If such an error arises because the instrument is affected by properties other

than the desired property of the material to be measured, then appropriate

modifications should be made to the instrument, auxilliary measurements should

be made by means of which the errors can be corrected, or a more appropriate

gage should be used. It is not recommended that a simple scaling of the value

assigned to the gage be made, since the sensitivity of an instrument to a property other than the one which it is designed to measure is usually not

stable in time. Generally, the use of gages cannot compensate for errors due

to an instrument's sensitivity to periferal properties, and often the use of

gages can introduce errors though this property.

In summary, there are two factors in a good gage measurement. First,

the gages must be accurately measured, and second, the measurement procedure

must be analyzed to be certain that the measurement is made in a way that

the property of interest is dominant in determining the instrument output.

Principally as a legacy from the policies of the section of NBS which

formerly handled this work, there are certain

H.3 SPECTROPHOTOfeRIC GAGES WHICH ARE CURRB1TLY SUPPLIED BY THE OPTICAL

RADIATION SECTION^ which win be described here briefly.

H.3.1 VITROLITE TILES (212. Uj. -o. (C. 3.58) ; C.3.59) are a white ceramic

material with a fire polished surface and are used as a standard gage for

diffuse reflectance. The main advantage of Vitrolite over other materials

is its uniformity, since it was originally manufactured in large quantities

as a building material. This material has been replaced in buildings by

enameled steel, plastic, and other materials, and as a result it has not been

manufactured for a number of years. The limited supply which NBS still has

on hand represents most of this material still in existence in a form useable

as gage material. In addition to its near extinction, vitrolite has several

other disadvantages. It is quite translucent, which causes the reflected

beam to eminate from a much larger area than is struck by the incident

beam, giving rise to "edge effects" difficulties in many cases (L.2.3).

These tiles are porous in their interior structure and as a result when the

surface is ground to a matte finish, which is desirable in some cases, it

cannot be cleaned. In addition to the intrinsic problems associated with

the material there are errors associated with the measurement of the master

standard (N.2.3, N.2.4), which errors, however, are to be corrected soon.

H.3.2 DIDYMIUM AlC HOLIIIUM OXIDE GLASS FILTERS (212. i4d. -i. (c. 3.58)) , which have

a number of sharp minima in their spectral transmittance , are used as wavelength

standards. These materials differ little from filter to filter and are very stable

both with respect to aging and thermal properties. The literature offered with

the holmium oxide filters, however, contains an extrapolation to zero bandwidth which implies use for more accurate wavelength calibrations than can actually be obtained. A more careful study of these materials may show that

they can be used for wavelength calibration without being measured glass by

glass as is presently done.

52
D-12

H.3.3 GU^ STOTARDS OF SPECTRAL TRAWITOJCE (2i2.i4a.-e. (c.s.ss)

(C.3.60) consist of four filters, carbon yellow, selenium red, cobalt blue

and copper green. They were chosen with the idea of allowing spectrophotometers

to be checked rapidly for linearity, the absence of stray light, etc. For

example, the cobalt blue has a strong absorption in the central region of

the visible spectrum, and transmits well in both the red and violet ends of

the spectrum. If an instrument measures the transmittance in this central

wavelength region properly, there is little chance that there is stray radiation

at either end of the spectrum, ^^hile these gages are quite useful within

the range of accuracy for which they were initially designed, they are not

adequate for many current applications.

As is pointed out in detail elsewhere (7.2.2b), the task of supplying

measured gages will be turned over to other groups in order that the IBS

spectrophotometry group can pursue the more basic tasks of standardization.

Since these gages have served as a basis for the measurement system for many

years, however, we plan to provide corrections for the kno^m errors in the

earlier measurement of these gages to the extent that one possessing such

a gage can correct its calibration to within the uncertainties initially claimed

by NBS.

In addition there are several

H.i| OTHER \^ GAGES RELJ\TE3 TO SPECTROPHOTOfETRY. chief among these are H.4.1 GLASS FILTERS FOR SPECTROPHOTOfTM (srm 930 (ca.ei)), a set of three

neutral density filters for checking linearitv;

LIQUID FILTERS FOR SPECTROPHOTOfOY (srm 931 (c.3.61)), the first m

a series for gaging certain absorption measurements; and

H.4.3 COLOR STATORDS FOR SPECTROPHOTaETER-TRISTIfULUS IilTEGRATOR SYSTE1S

(SRM 2101-2105 (C.3.61) ; (C. 3.62)) . The first two items are projects of IMR

under sponsorship of the clinical chemists, while the color standards were

developed by the IBS spectrophotometry section. Gold on glass and aluminum

on glass are offered as MA REFLECTANCE STATORDS FOR THE ULTRAVIOLH TO KIFRARED (srm 2001-2008;

(c.3.61)). These specular reflectance gages were measured in 1970 by the

Optical Radiation Section of IBS over the wavelength range 250-30000 nm.

In addition, other NBS gages and gage measurement services, such as for

photographic density step tablets (NBS Tests 212.135a, 212.135b, and 212.135c

(C.3.58)) and light sensitive papers and chips (SRM Nos. 700b, 701b, 702, 703

(C.3.61)) for fade testing, depend at least in part upon spectrophotometric

measurements

53
APPENDIX E. WHAT IS AN APPEARANCE MEASUREMENT?

It is not all obvious to the uninitiated just what is meant by

measuring color or measuring appearance. Nor is it obvious what can be

gained by doing so. To provide some background in this area, sections

5.1 and Appendix I from the 1972 report of the spectrophotometry study

by the IBS group are given here. Although the measurement of appearance

is carried out through spectrophotometric measurements in the general

sense in which they are defined in this report, this is only done after

psychophysical research provides a model by which one can interpret the

results of spectrophotometry in terms of what a human being will see. The responsibility within NBS for seeing to it that these psychophysical

models are kept up to date is not clearly defined, and the latter part

of Appendix I of the 1972 report is addressed to the question of what

involvement should NBS have in fixing these models and where should the

responsibility lie within NBS.

One can define the

5il APPEARAI^JCE °f object as the impression an object makes upon a person

through information conveyed to him by electromagnetic radiation and perceived

through his eyes. The appearance of an object to an individual depends upon

aspects of his judgement which have been based upon his past experience. As

a result, absolute quantification of the appearance of a given object is only

moderately successful. Similarly whether or not two objects which differ

distinctly in appearance will "go together" to produce a harmonious effect

on the observer depends upon his background and such "taste" will vary from

individual to individual. However, the ability of observers to judge whether

objects are alike is much keener, so that very small differences in appearance

can be recognized. Furthermore, individuals almost universally associate

small but noticeable differences in appearance with negative concepts such

as "worn", "faded", "unstable" and "carelessly or unskillfully made". For

this reason it is very important for manufacturer's of consumer goods to control

very carefully the appearance of products which might he placed together while

being sold or used. Either the objects must differ from each other in appearance

54
E-2

so much that it is obvious the difference is intentional or they must appear

enough alike that only the keenest observer could tell the difference. The

latter is the only practical approach in most cases.

With control of the appearance of products so important, there is a definite appeal to having

5.1.1 APPEARAlNCE KISTRUftiiTATION to assist in quality control. In the development of such instruments, appearance is first broken down into more tractable

aspects (I) such as color, pattern, texture, brightness, whiteness, opacity,

gloss and haze. A mathematical model must then be constructed to place a given

appearance aspect in one-to-one correspondence with measurable optical parameters

such as the spectral reflectance of an object and the spectral irradiance of

its surface. Since the manufacturer is not usually able to control the lighting

under which a product will appear, he must control the interaction of his product

with light wavelength by wavelength over the entire visible spectrum. As a result, most appearance measurements are being done spectrophotometrically

rather than by tristimulus colorimetry (I)

Because appearance is a human oriented field, one may well ask why a machine should do a man's job in observing appearance. In the past, human

observers exclusively judged appearance, but several things have led to a trend to replace these observers with instrumentation. The labor movement

has developed in such a way that tedious and exacting jobs of inspecting, such

as shading paint, with all of their responsibility for decision pay little more

than jobs which are far less demanding. This and certain psychological factors

make it more and more difficult to find people to take such jobs. Also, the

ability of a human observer to perceive differences can be affected by

psychological or physiological factors such as boredome, fatigue, or diet.

Therefore, it is becoming more common to use machines as observers. In the

future it will probably become common to close the control loop directly from

the instrument output, thereby completely automating the routine quality control

of appearance (J).

There are many

5.1.2 AREAS OF APPLICATION appearance instrumentation, some of which

have been exploited for some time and others which have been tried only recently.

Very few applications have been completely successful to date, and many are still far from successful, but the advantages to be gained from solving the

problems are great enough and the prospects of obtaining solutions are good

enough that many companies are active in the field, including several new ones. A trade association has recently been formed by manufacturers of appearance

instruments to further their common interests (K.3, L.2.10).

Color and gloss measurements have long been used successfully in

manufacturing paint and other finishes (C.3.3). Specifications for the

appearance of finishes used by the government as a whole have been drawn up

and newer versions will include spectral reflectance factor curves of the sample

colors as an aid to matching (C.3.4). This field has been considerably com- licated in recent years by the increased use of flake metal pigments (C.3.5)

which add an irregular angular and wavelength distribution to the reflectance

55
E-3

factor and causes it to differ from point to point on a surface. For such

measurements, the instrumentation will have to recognize texture or pattern

to produce an acceptable match (I)

A similar problem is faced in the textile industry. Color measurement

for sorting bolts of smooth textured solid colored material into lots for mass production of clothing is fairly successful, but smooth solid colors

account for only a small part of the textile market. An interest is developing

in instrumentation with pattern recognition capability for textiles (C.1.52),

and ultimately instrumentation for automated control of production (J)

There has long been a need for a means of communicating appearance from

architect to builder, and for work in predicting the finished appearance of

surfacing materials from the raw materials which go into them. This field has

been dormant for some time, but the need has remained and new activity on an organized level is under consideration. Prefinished interior and exterior

surfaces such as paneling, enameled steel, and decorative glass (C. 1.173) have

become more commonplace, allowing the architect to see the finish before the

structure is built. However, quality control of such materials must be excellent

in order to prevent a building's looking like a faded irregular checkerboard.

Also, in order that matching replacement panels can be provided later for repairs,

great demands are placed on appearance matching measurements either to communicate

a description of what is needed or to produce a replacement from earlier specifications. •

. ' . -

A rather unique mixture of spectrophotometry and spectroradiometry is

needed by the television industry for providing a means of translating the scene that the program director creates on his monitor screen into standardized

broadcast modulation signals. This, along with complementary work on color

reproduction in photographic films intended for television, is necessary in

order to provide the viewer with continuity in appearance as the programming

source is abruptly changed between live scenes from studio cameras, scenes from remote field cameras, taped segments, and filmed segments. The basic

procedures are being worked out through SMPTE and FCC cooperation, but the

standardization should be placed on an accurate basis through the help of NBS.

Recent advances in the technology of colorants and materials, while opening

the way to wider ranges of appearances which can be created, has produced

corresponding appearance measurement problems. The wider use of plastics

has created an urgent need for standard techniques to handle appearance measurement and specification of translucent materials (C. 1. 17 ,C. 1. 147) . New highly

stable organic pigments (C.3.6,C.3.7) have extended the range of colors which

can be produced, and at the same time have increased the potential difficulties

to be encountered with metamerism (I) . Fluorescent colorants have come into

wide use (C. 2 . 29 ,C. 2 . 87) , and methods of measuring and specifying the appearance

of such colorants is sorely needed (C. 1. 41 ,C. 1. 123) , but is only beginning to

be developed (C.1.53 ,C. 3.8) . Although it is far from complete, the coverage

given appearance measurements in this subsection, along with the discussions

of gloss (1.2.2) and haze (1.2.3) which appear elsewhere in this report.

56
E-4

should serve to illustrate the nature of the work to be done.

Many factors go into determining the

5.1.3 lEEDS FOR ACCURACY IN APPEARANCE feSURHei. two of these are the

complexity of the object being measured and the difficulties involved in

producing the object. For example, the color of ceramic tiles is rather easily

measured since the surfaces are smooth, the reflectance is not a rapidly

varying function of wavelength, there is not a large variety of colorants

available to be used, and a sample tile from a run makes an ideal gage for

future runs. However, the color of the tile depends upon the firing process

in a complicated way which is difficult to control. As a result, the measurements are generally more accurate than the process control, and ceramic tile

manufacturers are satisfied with the present state of the measurement system

(C.1.80). On the other end of the spectrum, the fabric finishers are dealing

with a product in which texture and pattern are as important as the color,

the dyes and inks used have a complex spectral variation with most of them

fluorescent, there is a huge number of colorants available to choose from,

and the resulting product is subject to rotting and fading so that it is not

a suitable gage. Needless to say, the textile finishers are not satisfied

with the present state of appearance measurements (C. 1 . 52 ,C . 1 . 158 ,Q . 2)

The need for a common basis of measurement in appearance becomes evident

as soon as one has a need to communicate quantitative information about

appearance as, for example, between buyer and seller (L.2.3) or between

designers and manufacturers. Numerical specifications on such items as the

color and gloss of paints, the color of cloth for uniforms, and the haze

of automobile window glass have long existed. As the performance of the

instruments improves, the number of such specifications goes up. The coil

coating industry is an example of a new area in which tight color and appearance

specifications have arisen. In this rapidly developing technology, metals are precoated with finish while they are still in the form of rolls or coils of

sheet, and the final product is stamped out of the finished metal. If

advantage is to be taken of this type of process, one must be able to depend

upon the appearance to be uniform from one part of a coil to another and from

coil to coil, and there must be a means of accurately specifying the appearance

of materials to be supplied.

Quantitatively, the accuracy required in appearance measurements is

based upon the ability of the eye to distinguish differences in appearance.

Although this is a complex subject in itself (I) , some quantitative estimates

of the accuracy needed can be made. In color, Hoffman (C.3.9) estimates that

each of the tristimulus values X, Y, and Z should be known to within 0.2% of

its value in order to make valid subjective assessments from the objective

data. Simon (C. 1.158) estimates that reflectance factors should be measurable

within 1% of their value at the 0.1 level for dark color color imetry. These

limits, which are in fair agreement and are within the levels of repeatability

currently being obtained, may have to be tightened by a factor of two or three

if the measurements are to be used for feedback in automatic process control.

The estimated inaccuracy of reflectance measurements, however, is an order

of magnitude greater than these limits, so that work will be required in this

57
E-5

field before the measurements will provide an adequate means of communication

in the field.

5.1.^ THE VALUE OF ACCURATE APPBWCE .i^URBE^JT to commerce iies m the area of quality control. After all other factors are taken into account (and

sometimes before) the buyer gravitates toward the better appearing product.

If U.S. industry is to maintain its share of the world market for consumer

goods, it must compete with the appearance of other goods as well as with their

performance. Furthermore, if U.S. industry is to compete with countries with

more favorable (to industry) labor conditions, it must automate, and the automation of finishing will require accurate instrumental appearance measurements

with a sound basis in human perception of appearance. This fact is being

recognized in many industrialized nations, notably by Japan through the Japan

Industrialization Planning Association (Q.3) which, among other things is seeking

to improve Japanese color technology and to fully automate fabric production

and quality control.

Other values of appearance measurement and control to society are difficult to place directly on a monetary basis. Except for a few obvious

safety applications involving road signs and automobile glass, the bulk of

appearance work is aimed at psychological impressions. The difference between

success and failure in dealing with appearance manifests itself in differences

between having things seem well-kept or shabby, well or poorly made, carefully

or poorly planned, harmonious or discordant —causing the beholder to have

feelings of well-being or to be ill-at-ease. In these times of rising population density, this will probably become an increasingly important aspect of our national life.

The size of the portion of the economy which is involved in appearance

is immense as is graphically expressed by Mr. Louis A. Graham in a recent letter

(Q.2-6) to the Secretary of Commerce requesting continued NBS activity in the

color field:

"a superficial consideration of the color industry might

lead you to believe that the multi-million dollar colorant

(dyes and pigments) industry and their suppliers might be

the only beneficiaries of NBS efforts in this field. This

is not true. The major beneficiaries will be the multibillion dollar color dependent industries such as textiles,

paint, automotive, furniture, packaging and others."

The future promises expansion, and the value of good standardization of

techniques and calibrations will expand correspondingly.

58
E-6

Appendix I

Background in Appearance

A large portion of this report (5.1) has been devoted to a discussion of

the uses of and needs for appearance measurements, but little has been said about

the technical aspects of the measurement process. There are two

I.l REAS(XJS FOR PRESENTIl^G BACKGROUilD information on appearance measurements.

First, although the appearance of objects is observed to some extent by all who

can see

1.1.1 THE WAYS lii mm APPEARA"^CE IS ^EASURED ARE M WIDELY KIWJ. Therefore,

the physical measurements are explained briefly in the first part of this

appendix, along with some details about how these measurements can be involved

in various applications. Second, from information gathered in the study of

spectrophotometry being reported here, it seems reasonable

1.1.2 TO SUGGEST THAT A STUDY OF APPEARAfJCE ftASURBCJTS BE UiTOTAKEf] regarding

the aspects of the measurements other than spectrophotometric . The reasons for

this suggestion and the type of study being suggested are presented at the end

of the appendix.

The whole of the experience of perceiving appearance has been broken into

several parts by making certain

Ii2 ABSTRACTI Of'jS from the experience. The abstractions presented in the following

portion of the appendix are not to be regarded as unique, but rather as examples

of present practice.

One of the more conspicuous aspects of appearance for an observer with normal

vision is

1.2.1 COLORy or difference in experience resulting from differences in wavelength reaching the eye. The summary of color measurement to be given here is

necessarily brief. For those wishing to pursue the subject further, an excellent

and easily comprehended introduction to the subject is given by Billmeyer and

Saltzman (C.3.63) and more details can be found in books by Judd (C.3.64) and

Wyszecki and Stiles (C.3.65), the NBS monograph by Nimeroff (C.3.66), and the NBS

special publication on Colorimetry (C.3.67).

It has been found empirically from psychological experimentation that a proper combination of three spectrally different sources of light can create

the experience of "matching colors", the matching being most easily done if each

source emphasizes a distinctly separate region of the visible spectrum (approximately 380 to 700 nm wavelength). From experimental studies of this effect,

three dimensional models of color vision have evolved. One such model, formally

adopted by the CIE, will be described here. As an example, consider the color

perception associated with a non-f luorescing diffusely reflecting object. For

convenience, the description of the light flux is broken into two parts — e(A),

a function of wavelength, X, representing the spectroradiometric properties of

the radiation illuminating the surface and a function r(A) representing the

spectral reflectance of the object's surface. The product of these two functions

represents the amount of light entering _t^he eye^. The response of the eye is

represented by a set of three functions x(A) , y(X) , and z(X) called spectral

tristimulus values (Q.9). These were adopted from an infinite family of equivalent functions by agreement, and have the features that y(A) is identically

59
E-7

the function used in photometry to represent the overall sensitivity of the

eye and that all three of the functions are positive definite. Three numbers,

called tristimulus values, are calculated as follows:

X = /e(A) r(X) x(A) dX

Y = /e(X) r(X) yiX) dX (Eqs. II)

Z = fe(X) r(X) z"(X) dX

(Mathematically, these numbers are classed as functionals. Thus, functional

analysis should provide a good means of solving certain problems in colorimetry

such as error limits (7.2.3).) The presence of fluorescence complicates the

analysis since r takes on the characteristics of a two dimensional transformation

matrix rather than being a simple weighting function, but the outcome of the

calculation is a set of three numbers, X, Y, and Z which still have the same

meaning. The basis of colorimetry is that any surface uniformly giving rise to

a given value of X, Y, and Z will, in similar circumstances, appear to have the same color and brightness as any other combination of surface and illumination

giving rise to the same value of X, Y, and Z.

Another aspect of appearance which is often abstracted is

Ii2i2 GLOSS/ which can be expeditiously introduced through the example of a painted surface. In a painted surface, multiple scattering and selective

absorption produces a diffused reflected light with which one associates "the

color of the paint". However, a small fraction of the radiation, usually about

five percent, does not penetrate to the pigment to be scattered but is reflected

specularly (Fresnel reflection) from the surface of the binder in which the

pigment is imbedded. This reflection is only slightly wavelength dependent,

and hence gives the same impression of color as the incident light. The gloss

value assigned to a surface is a measure of the regularity of this reflection

high gloss being "mirror like" and low gloss "dull". In current practice, gloss

is measured by projecting collimated light onto a surface at a specified angle

of incidence. The fraction of the light reflected into a small solid angle

centered on the direction of specular reflection is a measure of the gloss.

Ii2i3 HAZE is an abstraction made in an effort to describe "cloudiness" in

a material which should be transparent. In present measurements it is quantified

as the ratio of the amount of light diffusely scattered in the foreward direction

by the material to the amount of light transmitted "straight through" the

sample

Ii2i^ LIGHTNESS is a measure of the apparent ability of a material to diffusely

reflect light. Once the source of illumination is specified, the Y value of

Eqs. II can serve as a measure of brightness.

Ii2i5 WHITD^ESS/ the other hand, is a measure of the appearance of colorlessness

in diffuse reflection. A departure from whiteness could be characterized as a departure from constancy of the r(X) curve at a magnitude near 100%.

60
E-8

11216 PATTERN is the result of a highly organized arrangement of appearance

aspects such as color, gloss and

11217 TEXrUREy where texture is used to describe the "three dimensional" properties of surface appearance as recognized by the presence of shadows and

small-scale variations in gloss. A plaid is an example of a repetitive pattern

based mainly on color, whereas embossing produces patterns based principally

on texture.

Although abstractions such as those above seem straightforward enough, there

are a number of

1.3 CaPLICATiaJS IN APPEARANCE fEASURBEfTS. one cause of complications is one

of the same things which has given added impetus to spectrophotometry, namely,

1.3.1 DEVELOPFBTTS IN miJOLOGY.

The effects of such technological change can be illustrated in terms of

colorimetry. Since equality of integrals does not imply equality of integrands,

one can see from Eqs. II that it is quite possible under a given illumination to

have two objects with differing r(A) match in color. Such a color match is called

a metameric match and the difference will not be detected under the given illumination by either a human observer or a tristimulus colorimeter. However, under a different illumination, a color difference may be noticeable. In the early years

of colorimetry, metameric matches could be tolerated. Since the common forms of

illumination, incandescent lamps and sunlight, had similar and continuous spectral

distributions of radiant energy, and since the spectral reflectance functions of

natural and early synthetic colorants varied slowly with wavelength (C.3.68), one was unlikely to produce a metameric match accidentally in which the r(A) curves differed greatly. As a result, adequate quality control could be maintained

through tristimulus matching under sunlight and incandescent light. This is no longer the case, however. The newer synthetic colorants have strongly varying

spectral reflectance and many of them fluoresce, either subtly or strongly (C.3.69).

Thus it is quite easy to produce a metameric match in which the two r(X) functions

differ strongly. Furthermore, new sources of light are being developed which depend

on arc discharges and phosphors producing illumination which is rich in line

structure and which has non-thermal continuum distribution. As a result of these

differences, objects which match metamerically under one illumination can distinctly

differ in color under another illumination. The implication of these developments

is that tristimulus colorimetry (visual or instrumental) is becoming inadequate

for quality control, and that control of r(X) by spectrophotometric means will be

essential. For the same reason, specifications of color should be based on a spectrophotometric rather than a colorimetric basis.

The spectrophotometry group of NBS can contribute to the success of color

quality control in two ways, first by seeing that the spectrophotometric measurement

system is maintained at a satisfactory level of accuracy and second by developing

procedures for determining limits of colorimetric error from spectrophotometric

data. This will involve a generalization of procedures developed in earlier work

(C.3.70, C.3.71), to include means of dealing with new colorants, new illuminants

and perceptual sensitivity to color difference. The mathematical bases for such

computations are closely related to those using observations at several wavelengths to solve the problem of specificity in chemical determinations (5.2.2,7.2.3).

The same type of mathematical procedures can also be used to handle color formulation problems, efficient measurements for control of color processes, and color

61
E-9

rendering measurements on sources of illumination (C.3.72). The color rendering

measurements, which formerly have been based on a finite set of test samples, may

need to be generalized to the entire color space in order to properly handle the new light sources and colorants. Concepts for such a generalization will also be

useful in developing special variations of the color rendering indices as suggested

by Judd (C.3.73). In fact, since efficiency of lighting is of prime importance

in conserving power, color rendering properties of the lamps may have to be com- promised in the process. This may place the burden on the colorant manufacturers

to produce colorants the appearance of which is less sensitive to variations in the

spectrum of illumination. The measure of this sensitivity, which might be called

a "rendering color" index, could also be determined with the same type of

mathematical procedure.

Naturally, color is not the only measurement which is affected by the

mushrooming of technology. In general, the variety of surfaces being manufactured

is increasing factorially with the introduction of new materials and finishing

techniques. A combination of this increase in variety of products and the need

to move to instrumental inspection has led to increasing recognition of the

1.3.2 IfiADEQUATE DEFLATION OF T!€ ABSTRACTIONS. Although gioss is related to

specular reflection, it is by no means as simple as the definition of 1.2.2 might

appear. The sparkle of plastic films, the glitter of metal flake top surfacing,

and the luster of metallic paints not to mention the visual effects produced by

plush fabrics and satin-like materials all belong in the category of gloss to some

extent. In a 1937 paper on the subject (C.3.74), Hunter defined five different

aspects of glossiness and specific measurements which correlated with each.

Several procedures for measuring gloss-related parameters have since been adopted

by standards organization, the latest being a two parameter technique adopted in

1967. Difficulties in obtaining correlation between the measurements and the

desired appearance aspects still exist, however, and some sort of pattern recognition

instrumentation may be required to solve the problem. (Earlier visual methods used

clarity of reflected image as an indicator of certain aspects of gloss.) The

problem is almost certainly one of definition, however, since brute force refinement of instrumentation, even to the point of requiring state of the art machining

and alignment in the instruments (C.3.79), has not solved the problems. Needless

to say, just what is meant by "pattern" and "texture" in appearance measurement

terms is even more vague than gloss.

It should be borne in mind that what is being described here is not semantics,

but a real problem in defining much needed measurements. Blemishes in appearance

are just as damaging to trade whether they result from poor measurement practice

or from poor definition of the measurement. Well defined measurements of appearance

are needed for communication between buyer and seller, for specifications, and to

allow items from next week's or next month's production run to be sold on the same counter as those made today.

Appearance measurements are also important in monitoring quality of production, but this implies another complication, the

1.3.3 NEED TO DEFINE DIFERENCES IN APPEARANCE. Tolerances must be established

for allowable differences in appearance in order to balance cost of production

against acceptability of the final product. Mathematically, differences in measured

values can be related to distances in the space in which the measurement is

described. Ideally, equal distances in the space in which the measurement is

described would represent equal impressions of appearance difference to a viewer.

In this way, tolerances could be placed on measured difference values for various

62
E-10

purposes. Differences between the measures of appearance abstractions are by

logical necessity more poorly defined than the measures themselves, and in

reality, with the exception of color differences (C.3.76), the differences are practically undefined.

The discussion above has wandered well out of the

I.^ BOTS OF SPECTROPHOMETRY. As defined in section 2 of this report,

spectrophotometry is a means of measuring the interaction of radiation with

matter. Spectrophotometric measurements, once defined, are physical measurements

with differences definable in physical terms. Appearance measurements differ from

what are considered purely physical measurements in two important ways:

a. The concepts are not as easily isolated within the

mind. The "primitive" concepts of distance connecting

places, time connecting events, and objects being "made

of something" were considered self-evident, objective

concepts, and they formed the basis for the heirachy of

classical physical science. These concepts serve well

for most pragmatic uses, even though modem physics has

shown that the choices were not as objective as they first

seemed. The concepts of appearance, by contrast, are more complicated and have always been regarded as subjective

and a part of the realm of psychology or psychophysics

b. The physiology of the human being is involved directly

in appearance measurements. Spectrophotometric properties

such as reflectance or transmittance can be defined on a purely physical basis, but defining appearance involves the

eye, its structure, and its function.

Spectrophotometry plays two roles in appearance measurement. First, it supplies

psychologists and physiologists with accurate knowledge of the optical properties

of samples which they use in experiments to define appearance. Once an appearance

measurement is defined, it becomes a physical measurement and spectrophotometry

is used as discussed in section 5.1 and the first part of this appendix.

Several

1.5 FACTORS SUGGESTIi^G A STUDY OF i^S m IBS IfJVOLVEflBTr III APPEARAfCE fEASURETBJT

were deduced from information gathered in the spectrophotometry study. From a practical standpoint, the measurements appear to be

IiSil URGBTTLY lEEDEDi U.S. manufactured goods are facing ever stronger competition

in the marketplaces of the world. Our general attitudes favoring high productivity

and opposing tedious labor point to automation and instrumentation. If specific

assistance should be required of NBS in appearance measurement, the initial part

of it will be needed in the next several years. If the U.S. is to gain the necessary

advantage from these measurements, we must be ahead of the rest of the world in

their development and use. 1.5.2 GOOD SPECTROPHOTOfETRY IS HOT SUFFICIBIT for defining appearance measurements,

it is only good for carrying them out. Psychological experiments and an understanding of the physiological functions of visual perception are necessary for

defining measurements which correlate well with the desired appearance aspects.

Such good correlation is abviously needed for efficient and effective use of the

measurements, but there is an additional advantage for doing the measurements

properly from the outset. If they are well defined and effective, they will be

worked into international standards with little change. The advantages of having

63
E-11

to change only a little to meet international standards are obvious.

1.5.3 RESPaiSIBILITY FOR APPEARANCE MEASURE€f1TS AT m IS POORLY DEFINED.

When the Metrology Division was dissolved, the colorimetry section was transferred

to lAT (Q.IO), where its activity in providing measurement definition underwent

de facto disassembly. No activity was instigated elsewhere in NBS to replace it,

and there is no evidence that a careful study has been made to determine whether

such an activity is needed.

1.6 OBJECTIVES OF AfJ APPEARAfJCE STUDY, if one is undertaken might include the

following

1.5.1 DETERfllMING THE MEEDS IN IMDUSTRY overall. Smce the fleld is presently

somewhat fragmented, such a determination must be made by a person or persons

knowledgable both in the psychology and physiology of appearance and in modern

methods of instrumentation who can deduce the real needs from the bits and

pieces of evidence which can be obtained and who can foresee the reasonable future

of such measurements. From such evidence the justification for support can be

determined

1.5.2 DETERflllJING THE SIZE OF THE TOTAL FFORT which win be required to develop

the needed measurements.

1.6.3 DETERMINING WHAT THE fOTRE Aff EXIEff OF N.BS m IBS IfWOLVBWT SHOUUD BE.

It may be that these should be nil, but this is really doubtful. A few incidental

findings from the spectrophotometry study provide some indications of what this

involvement should be like.

a. The NBS program should be efficiently directed toward

developing general descriptive models of the process of

visual perception from which solutions to pragmatic measurement problems can be sensibly derived. The recent advances

in instrument and component technology (F,G) make it practical

' to build instrumentation with the sensitivity of the eye and

which has pattern recognition capability. In order to take

advantage of this technology to solve important problems

in appearance measurement ( J ,R. 2 . 1 ,R. 2 . 2) a thorough

quantitative understanding of the mechanisms and limits of

visual perception are necessary.

, b. The NBS program should provide leadership in developing

foundations of appearance measurements. It should not, however,

become involved in specific applications, per se, since these

are too numerous and fragmented. In particular, NBS should

establish a reasonable measure of distance for each general

measurements space which is defined (1.3.3) in order to provide

uniformity in the measurement system, but it generally should

not become involved in the details of establishing the

tolerances for acceptability in particular products (with

the possible exception of government procurement specifications)

c. The person or group which does the work should be

thoroughly grounded in physics, psychology, physiology,

metrology, and modern instrumentation methods and also be

able to develop and maintain a no-nonsense program directed

toward pragmatic appearance measurement procedures. This

combination will not just happen.

64
E-12

To the outside world it appeared that NBS had dropped appearance measurement

by default. This has caused concern among the users of such measurements which

has often been expressed, some of these expressions appearing in the letters in

Q.2. This concern was somewhat relieved x^7hen the spectrophotometry study was undertaken, but concern about the basic foundations of appearance measurement

still exists in the technological community. The writer of this report shares

this concern.

65
F-1

APPENDIX F

REFERENCES

The following list of references is appendix C from the 1972 report

of the study of the spectrophotometric measurement system by the IBS group.

Since this list was prepared, the writer has made several dozen new contacts

and a number of good articles on spectrophotometry have been published. However, this list will still serve to illustrate the extent of the background

work which went into the study as well as listing most of those contributing

to the study. The contributions of the writer's more recent contacts is

gratefully acknowledged.

66
F-2

Appendix C (From 1972 Report)

References

A large fraction of the

Cil IlJDIVIDUALS contributing information on which the conclusions of this

study are based are named in this list. An effort was made to limit the list

to the principal contacts, those with highly responsible positions in technology,

sales, or management or whose contribution to spectrophotometric measurement

is significant. A few of the principal contacts may have been omitted unintentionally. In addition, of course, there were many who contributed through group

conferences and discussions who have not been listed here specifically. Their

help is gratefully acknowledged.

The contributions were made for the most part through direct discussions,

but a few contributed through letters to us or through delivering particularly

informative lectures or seminars which one of us attended. Whenever a specific

reference to an individual is made in this report, it is denoted by C.l followed

by the number of the name in the list. For example, a reference to Dr. Abel

would be indicated by (C.1.1).

1. Abel, Dr. Peter G. ; (C.2.72a) Calibration of Satellite Remote

Sensing

2. Alden, Alex; (C.2.92) Overview of SMPTE Work

3. Alexander, John W. ; (C.2.48) Use of Spectrophotometry in Chemical

Manufacturer's Laboratory

4. Andrus, W.E. ; (NBS:400.04) NBS Programs and Policy

5. Askew, John R. ; (C.2.102) Jet Engine Smoke Emission Tests

6. Atkins, Joseph T. ; (C.2.32b) ISCC Spectrophotometry Round Robin

7. Austin, Jack; (C.2.44b) Textile Properties

8. Auth, Jerry; (C.2.36) Applications of Infrared Measurements to

Military Problems

9. Babb, Raymond; (C.2.59) Agricultural Colorimetry

10. Bader, William F. ; (C.2.68) Abridged Spectrophotometry in Process

Control

11. Bartky, Dr. Ian R. ; (NBS:400.00) Plans and Activities of lAT

12. Bennet, Dr. J. M. ; (C.2.65) Measurement Techniques

13. Bennett, Dr. Harold E. ; (C.2.65) Thin Film Reflectance Measurements

14. Bertero, Edward P.;(C.2.71) Standardization of Color Television Systems

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F-3

15. Billmeyer, Fred W. ; (C.2.88) Colorimetry

16. Blackman, W. ; (C.2.77) IR Measurements

17. Bostick, Ronald E. ; (C.2.89) Measurement of Translucent Materials

18. Brackett, Frank ; (C . 2 . 101) Color Film Processing

19. Brewer, Glen A.; (C.2.99) Pharmaceuticals

20. Brezinski, Dr. J. P.; (C.2.52) Optical Measurements for Paper

21. Bruening, Robert J.; (NBS:221.12) Photodetector Calibration

22. Brumfield, Robert ; (C . 2 . 29) Fluorescent Colorants

23. Budde , W. ; (C.2.93) Diffuse Reflectance Measurements

24. Burke, Dr. Robert W. ; (NBS:310.04) Absorption Measurements for

Liquid Gases

25. Cattaro, Matthew; (C.2.18) Instrumentation

26. Charvat, Robert A.; (C.2.48) Pigments

27. Christie, John S.;(C.2.31) Appearance Instrumentation

28. Clarke, F.J.J. ; (C.2.74) Spectrophotometric Gages and Measurements

29. Coulter, Jack; (C.2.10) Measurements for Military Applications

30. Conner, William; (C.2.35) Smokestack Emission Measurements

31. Cravitt, Sam; (C.2.37b) Fluorometry

32. Dearth, Leonard; (C.2.52) Paper Appearance Measurements

33. Derby, Roland; (C.2.30) Colorimetry in Industry

34. Dickson, George R. ; (NBS:311.05) Opacity Standards for Dental Ceramics

35. Douglas, C.A. ; (NBS:221.12) Retroreflectance

36. Dummer, Richard; (C.2.42) Spun Epoxy Mirrors

37. Eckerle, Kenneth L. ; (NBS:221.12) High Accuracy Spectrophotometry

38. Elstad, John; (C.2.68) Retroreflectance

39. Erb, Wolfgang; (C.2.85) Absolute Reflectance

40. Fancy, Robert; (C.2.62) Monochromators , High Resolution Spectrophotometry

41. Fertig, Lloyd; (C.2.23) Specifications for Fluorescent Pigments

68
F-4

42. French, Judson C. ; (NBS:425.02) Photoconductor and Microelectronics

Measurements

43. Fuchs, Dr. Jacob; (C.2.9) Spectrophotometry in Chemistry

44. Galloway, William; (C.2.14) Immersed Filters as Linearity Gages

45. Geist, Jon C. ; (NBS:221.12) Reflectance Measurements, Detectors

46. Giesecke, Paul M. ; (C.2.3) Absolute Diffuse Reflectance

47. Gilmore, John; (C.2.62) Monochromators

48. Glen, Jerry; (C.2.82) Coordination of Measurements in a Large Industry

49. Goebel, David G. ; (C.2.81) Measurement Techniques

50. Goldman, David T. ; (NBS:200.00) NBS Programs and Budget

51. Gordon, Louis I.; (C.2.79) Measurement of Nutrients in Sea Water

52. Graham, Louis A.; (C.2.16) Textile Colorimetry

53. Grum, Franc; (C.2.34) Fluorescence, Lighting Materials

54. Haenni, Dr. E.O. ; (C.2.39a) General Chemical Measurements

55. Haller, Dr. Wolfgang K. ; (NBS:313.02) Glass

56. Halvorsen, Gary; (C.2.59) Agricultural Colorimetry

57. Hamilton, James M. ; (C.2.92) Infrared Instrumentation

58. Hammond, H.K., III; (NBS: 411. 04) Reflectance Measurements

59. Hammon, H.K., IV; (C.2.41) Instrumentation

60. Hanes, Dr. Randall M; (C.2.54) Colorimetry

61. Hanst, Dr. Phil; (C.2.35) Multiple Pass Spectrophotometry

62. Harris, Chester; (C.2.31) Instrumentation

63. Hawes, Roland C. ; (C.2.17) Standardization

64. Haupt, Mrs. Geraldine ; (NBS :221. 12) Colorimetric Gages and Visual

Colorimetry

65. Heck, Patrick; (C.2.82) Industrial Spectrophotometry

66. Hemmendinger , Henry; (C.2.49) Calibration

67. Hilleary, D.T.; (C.2.72) Satellite Reflectance Standards

69
F-5

68. Hillman, R. ; (C.2.91) Colorimetry in Retail Trade

69. Hoffman, J. Gordon; (C.2.50) Needs for Improved Measurements

70. Holton, A.B.; (C.2.93) Overview of Paint Industry

71. Hooper, Page; (C.2.17) Instrumentation

72. Howard, Paul T. ; (NBS:421.04) Paint Reflectance Standards

73. Howett, Dr. Gerald L. ; (NBS:421.14) Color Vision

74. Hsia, Dr. Jack J.; (NBS:221.12) Reflectance, Color Differences

75. Huey, Dr. Sam J.; (C.2.93) Color Control in Paint Production

76. Hunter, Richard S.; (C.2.51) Appearance Measurements

77. Ingle, George; (C.2.69) Industrial Applications

78. Jakubowski, James; (C.2.108) Graphic Reproduction

79. Jasinski, John; (C.2.82) Glass Technology

80. Johnson, Dr. Gordon H. ; (C.2.38) Inorganic Colorants, Ceramics

81. Johnson, Norbert L. ; (C.2.68) Retroref lectance

82. Johnston, Ruth M. ; (C. 2.56a) Color Formulation

83. Jones, J. Grayson; (C.2.26) Color Television Monitors

84. Joseph, Meyer; (C.2.46b) Government Purchase of Paints

85. Kallet, Eli A.; (C.2.37b) Fluorometry, Stable Arc Sources

86. Kaskey, Gaden; (C.2.59) Agricultural Colorimetry

87. Kaye, Dr. Wilbur; (C.2.14) Instrumentation

88. Keane, Thomas J.; (C.2.41) Instrumentation, Gages

89. Keller, Charles; (C.2.14) Instrumentation

90. Keller, Elaine; (C. 2.56a) Color Formulation Systems

91. Kelly, Kenneth L. ; (NBS:421.14) Colorimetry

92. Kenyon, George; (C.2.17) Instrumentation

93. Koplito, Richard E. ; (C.2.46a) Government Procurement

94. Kostkowski, Dr. H. J. ; (NBS:221.12) Optical Radiation Section Policy

70
F-6

95. Kurth, Ralph; (C.2.82) Long Path Measurement in Glass

96. Lashof, Dr. Theodore W. ; (NBS:411.03) Collaborative Reference Program

97. Leete, Charles W. ; (C.2.60) Appearance Instrumentation Industry

98. Lewis, Dr. T.E.; (C.2.32a) Dyes

99. Levy, Dr. Gabor B. ; (C.2.84) Instrumentation

100. Lockhart, Wayne C. ; (C.2.20) Tuneable Dye Lasers

101. Locklin, Paul ; (C . 2 . 87) Fluorescent Colorants

102. Loeb, Harry; (C.2.108) Instrumentation

103. Luckern, Paul; (C.2.55) Spectrophotometry in Drug Patents

104. Ludwig, Klaus; (C.2.42) Many-pass Instrument

105. Lusk, Thomas E. ; (C.2.43) Colorimetry in Lighting

106. Madden, Dr. Robert P.; (NBS:232.03) Former Activities of NBS

Spectrophotometry Section, Instrumentation

107. Malthouse, David; (C.2.61) Instrumentation

108. Manning, Robert; (C.2.14) Instrumentation

109. Margesen, John; (C.2.35) Sulfur Dioxide Determination

110. Marciniak, Michael; (C.2.70) Absolute Reflectance, Color

111. Marsh, Jack; (C.2.105) Fluorescence

112. Martin, Robert; (C.2.32a) Dye Chemistry

113. Mavrodineanu, Dr. Radu; (NBS: 310. 04) Analytical Chemistry, High

Precision Spectrophotometry

114. Maynard, A.W. ; (C.2.67) Spectrophotometric Identification of Metals

115. McCamy, Calvin S. ; (C.2.56b) Measurement Techniques

116. McClinney, Dr.; (C.2.35) Long Path Measurements, Dye Lasers

117. Menis , Dr. Oscar; (NBS:310.04) Analytical Chemistry Spectrophotometry

Program

118. Michaels, Theodore D. ; (C.2.63, C.2.83) Reflectance of Pharmaceutical

Powders

119. Mielenz, Dr. Klaus D. ; (NBS:310.04) Optical Design

71
F-7

120. Miller, V.F.; (C.2.89) Heat Transfer Through Plastics

1:21.- Mitteldorf, Mr. Arthur; (C.2.97) Fluorometric Instruments

12.2. Molter, R.C.; (C.2.57) Measurements in Glass

123. Morehead, Walter E. ; (C.2.86) Fluorescent Brighteners

124. Meunier, Dr. Paul L. ; (C.2.32a) Dye Production Quality Control

125. Nader, John; (C.2.35) Source Emissions

126. Neu, Mr. J. Turney (C.2.42) Bidirectional Reflectance

127. Neubrech, David A.; (C.2.41) Instrumentation

128. Nimeroff, Isadore; (NBS:221.12) Colorimetry

129. Norris , Karl H. ; (C.2.1) Spectrophotometric Evaluation of

Agricultural Products

130. Norris, Robert W. ; (C.2.78) Reflectance Measurements on Paint

131. O'Connor, John; (C.2.39c) Retroref lectors

132. Oellrich, Dick; (C.2.50) Secondary Standards, Instrumentation

133. O'Keaffe, Andrew; (C.2.35) Environmental Monitoring

134. Owens, Paul; (C.2.42) Drug Patents

135. Popenoe, Charles; (NBS:221.12) Automation

136. Popsen, S. J. ; (C.2.61) Instrumentation

137. Prior, Paul; (C. 2. 107a) Target Signatures

138. Rendino, John; (C.2.62) Monochromator

139. Rib, Dr. Harold T. ; (C.2.104) Quantitative Measurement in Remote

Sensing

140. Rich, R.B.; (C.2.28) Exhaust Smoke Measurement Senior Engineer,

Instrumentation

141. Richard, Steve; (C. 2. 107b) IR Transmlttance

142. Richmond, Joseph C. ; (NBS:221.12) Reflectance, Ceramics

143. Rittner, Dr. Edward; (C.2.24) Heat Transfer

144. Robertson, Dr. Alan R. ; (C.2.73) Goniophotometry

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F-8

145. Robinson, Roland D. ; (C.2.90) Appearance Measurements

1A6. la Rocca, Jerry; (C.2.66) Remote Sensing, Goniophotometry

147. Rosenthal, Robert D. ; (C.2.76) Instrumentation, Agricultural Uses

for Spectrophotometry

148. Sanders, Dr. C.L. ; (C.2.73) Detector Calibration

149. Schaeffer, W.D. ; (C.2.45) Research Director, Graphic Arts Colorimetry

150. Schleter, John C. : (NBS:431.00) Activities of NBS Spectrophotometry

Section

151. Schroeder, Norm; (C.2.15) Infrared and Ultraviolet Calibrations

152. Schwab, Hans J.; (C.2.21) Spectrophotometry in Sales and Production

of Chemicals

153. Seabright, Dr. Clarence; (C.2.48) Ceramic Colorants

154. Sellers, Dr. D.E. ; (C.2.69) Need for Inter-Laboratory Agreement

155. Shaw, Roderick K. ; (C.2.40) Food Quality and Appearance

156. Silkman, Mr.; (C. 2. 107c) Photographic Materials

157. Sillag, F.C. ; (C.2.13) Stack Emission Measurements

158. Simon, Frederick T. ; (C.2.22) Textile Finishing

159. Sink, B.R. ; (C. 2. 107a) Target Signatures

160. Siranni, J. Donald; (C.2.47) Production Control

161. Smith, John T. ; (C.2.72b) Colorimetry and Densitometry in Mapping

162. Smith, Richard; (NBS: 271. 02) Laser Power Meters

163. Steiner, Dr. B.W. ; (NBS:221.12) CORM, Radiometry and Photometry

Sensing

164. Stenius, Ake S:son (C.2.100) Absolute Diffuse Reflectance

165. Stensby, Per; (C.2.21) Visual Fluorescence Evaluation

166. Stepchuk, Zenon ; (C.2.68) Instrumentation

167. Stevison, Donald F. ; (C. 2. 107b) Materials Research

168. Stewart, James E. ; (C.2.33) Biophysical Measurements

169. Stewart, Michael; (C.2.8) Garment Production

73
F-9

170. Steirwalt , D.L. ; (C.2.75) Infrared Measurements and Information

171. Strieby, Robert A.; (C.2.24) Needs for Infrared Measurements

172. Suga, Nagaichi; (C.2.103) Gloss and Haze Measurements and Standard

Gages

173. Swift, Dr. Howard R. ; (C.2.57) Specular Measurements, Glass

174. Takkunen, Bill; (C.2.68) Instrumentation

175. de Torres, Manuel; (C.2.64) President, Colorimetry in Advertising and

Printing

176. Tripp, Robert W. ; (C.2.37a) Linear and Angular Encoders

177. Trumble, Capt. Kenneth C. ; (C.2.107a) Target Signatures

178. Turner, G.K.; (C.2.105) Fluorometry, Instrumentation

179. Ulrich, Dr. William; (C.2.14) Instrumentation

180. Valez , Michael; (C.2.14) Instrumentation

181. Van Fleet, Mr.; (C.2.44b) Textile Production

182. Velapoldi, Dr. Ranee A.; (NBS:310.04) Spectrof luorometry

183. Weidner, Victor R. ; (NBS:221.12) Infrared Measurements

184. Weissler, Dr. Alfred; (C.2.39a) Cosmetics

185. Werner, Alan J.; (C.2.27) Filters

186. Wernicke, Bruno; (C. 2. 107a) Target Signatures

187. Wilcox, John; (C.2.34) High Density Measurements

188. Willey, R.R. ; (C.2.106) Infrared Instrumentation

189. Winters, William; (C.2.77) IR Measurements

190. Wood, Dr. L.A.; (NBS:311.00) Fading Tests for Dyes

191. Worley, Robert; (C.2.98) Textiles

192. Yates, Harold; (C.2.77a) Reflectance Gages for Use in Satellites

193. Yeatman, John N. ; (C.2.39a) Food Colorants

194. Yonemura, Dr. Gary; (NBS:462.02) Psychology and Physiology in Color

Vision

195. Zissis, George; (C.2.66) Remote Sensing

74
F-10

A number of the

Ci2 ORGAf^IZATIOf^S which contributed to the conclusions reached In this study

are listed In this section. An asterisk by the name of an organization Indicates

that It was visited by a member of our group during the source of this study.

Information was obtained from the other organizations through contacts with

representatives or through letters, brochures, catalogs, tech notes, or advertisements. This list also serves as an address list for the Individuals

named In C.l. References to this list are indicated by C.2 followed by the

number locating the organization in the list. For example, the U.S. Department

of Agriculture would be indicated in the text by (C.2.1).

1. ^Agriculture , U.S. Department of

Instrumentation Research Laboratory

Market Quality Research Division

Beltsvllle, Maryland 20705

(301) 474-6500

2. American Association of Textile Chemists and Colorlsts

AATCC Technical Center

P.O. Box 12215

Research Triangle Park

North Carolina 27709

(919) 549-8141

3. ^American Cyanamlde Co.

1937 West Main St.

Stamford, Conn. 06904

(203) 348-7331

4. American Instrument Co.

8030 Georgia Avenue

Silver Spring, Md. 20910

(301) 589-1727

5. American National Standards Institute, Inc.

1430 Broadway

New York, N.Y. 10018

(212) 868-1220

6. The American Society of Photogrammetry

105 N. Virginia Avenue

Falls Church, Virginia 22046

(703) 534-6617

7. *American Society for Testing and Materials

1916 Race St.

Philadelphia, Pa. 19103

(215) 569-4200

8. Apparel Research Foundation, Inc.

1120 Connecticut Ave. N.W.

Washington, D. C. 20036

(202) 233-2517

75
F-11

9. ^Arizona State University

Chemistry Department

Tempe , Arizona 85821

(602) 965-3462

10. *Army, U.S.

Mobility Equipment Research and Development Center

Night Vision Laboratory

Fort Belvior, Va. 22060

(703) 664-6071

11. Atlantic Research Corporation

3333 Harbor Blvd.

Costa Mesa, California 92626

(714) 546-8030

12. Avco Everett Research Laboratory

2385 Revere Beach Parkway

Everett, Mass. 02149

(617) 389-3000

13. Bailey Meter Company

Wickliffe, Ohio 44092

(216) 943-5500

14. *Beckman Instruments, Inc.

2500 Harbor Blvd.

Fullerton, California 92634

(714) 871-4848

15. *Bendix Aerospace Systems Division

3300 Plymouth Road

Ann Arbor, Michigan 48107

(313) 665-7766

16. Burlington Industries Research Center

P.O. Box 21327

Greensbora, North Carolina 27420

(919) 379-3240

17. *Cary Instruments

2724 S. Peck Road

Monrovia, California 91016

(213) 446-7181

18. Cattaro Scientific Controls

Rt. 1, Box 236,

Chantilly, Va. 22021

(703) 471-4131

19. Chicago Miniature Lamp Works

4433 N. Ravenswood Ave.

Chicago, 111. 60640

(312) 784-1020

76
F-12

20. *Chromatix

1145 Terra Bella Ave.

Mountain View, Ca. 94040

(415) 969-1070

21. Ciba-Geigy, Inc.

Geigy Industrial Chemicals

Ardsley, New York 10502

(914) 478-3131

22. *Clemson University

Textile Department

Clemson, South Carolina 29631

(803) 656-3177

23. Color-Vu Corporation

45 West 13 Street

New York, N.Y. 10011

(212) 924-2036

24. Colspan Environmental Systems, Inc.

P.O. Box 3467

oulder, Colorado 80303

(303) 449-4411

25. Comsat Laboratories

Linthicum Road

Clarksburg, Md. 20734

(301) 428-4541

26. *CONRAC Corporation

Video Monitor Group

Covena, California 91722

(213) 966-3511

27. Corning Glass Works

Corning, New York 14830

(607) 962-4444

28. Cummins Engine Co. , Inc.

Columbus, Indiana 47201

(812) 372-7211

29. *Day-Glo Color Corp.

4732 St. Clair Avenue

Cleveland, Ohio 44103

(216) 391-7070

30. *Derby Co.

49 Blanchard St.

Lawrence, Mass. 01842

(617) 683-8726

77
I F-13

31. *Diano Corp.

P.O. Box 347

75 Forbes Blvd.

Mansfield, Mass. 02048

(617) 339-3701

32. Dupont

a. *E. I. du Pont de Nemours & Co.

Organic Chemicals Department

P.O. Box 386

Wilmington, Delaware 19899

(609) 299-5000

b. E. I. du Pont de Nemours & Co.

P.O. Box 1217

Parkersburg, West Virginia 21601

(304) 863-5311

33. *Durrum Instrument Corp.

3950 Fabian Way

Palo Alto, California 94303

(415) 321-6302

34. Eastman Kodak Company

Research Laboratories

Rochester, New York 14650

(716) 458-1000

35. ^Environmental Protection Agency

Technical Center

Research Triangle Park

North Carolina 27711

(919) 549-8411

36. *Eocom Corp.

4630 Campus Drive

Newport Beach, California 92660

(714) 540-8453

37. Farrand

a. *Farrand Optical Co.

117 Wall Street

b. *Farrand Controls, Inc.

115 Wall Street

Valhalla, New York 10595

(914) 428-6800

38. *Ferro Corp.

Research Center

7500 E. Pleasant Valley Rd.

Independence, Ohio 44131

(216) 641-8580

78
F-14

39. Food and Drug Administration

*a. Division of Colors and Cosmetics

(202) 962-2470

*b. Division of Chemistry and Physics

(202) 962-0744

c. Bureau of Product Safety

Washington, D. C. 20204

(301) 496-7668

40. Florida Canners Association

P.O. Box 780

Winter Haven, Fla. 33880

(813) 293-4171

41. ^Gardner Laboratory

5521 Landy Lane

Bethesda, Maryland 20014

(301) 656-3600

42. ^General Dynamics /Convair

San Diego, Calif. 92112

(714) 279-7301

43. General Electric Co.

Nela Park

Cleveland, Ohio 44112

(216) 266-2339

44. Greenwood Mills, Inc.

a. P.O. Box 117

Greenwood, S.C. 29646

(803) 229-5311

*b. Ill West 40th St.

New York, N.Y. 10018

(212) 695-2626

45. Graphic Arts Technical Foundation, Inc.

4615 Forbes Avenue

Pittsburgh, Pennsylvania 15213

(412) 621-6941

46. GSA

a. Research and Testing Branch

Federal Supply Service

GSA Region 10

Auburn, Washington 98002

(206) 833-6500

b. Technical Operations Branch

FMQO

Federal Supply Service

Washington, D. C. 20406

(202) 557-7550

79
F-15

47. GTE Sylvania

Precision Materials Group

Chemical and Metallurgical Division

Towanda, Pa. 18848

(717) 265-2121

48. *Harshaw Chemical Co.

1945 E. 97th St.

Cleveland, Ohio 44106

(216) 721-8300

49. *Hemmendinger Color Laboratory

R.D. Pequest Bend

Belvidere, N.J. 07823

(201) 475-2123

50. Hoffman Engineering Corporation

183 R Sound Beach Ave.

Old Greenwich, Connecticut 06870

(203) 637-1719

51. *Hunter Associates Laboratory Inc.

9529 Lee Highway

Fairfax, Virginia 22030

(703) 591-5310

52. ^Institute of Paper Chemistry

Appleton, Wisconsin 54911

(414) 734-9251

53. ISOMET

103 Bauer Drive

Oakland, N.J. 07436

(201) 337-3811

54. Johns Hopkins University

Applied Physics Laboratory

8621 Georgia Avenue

Silver Spring, Maryland 20910

(301) 953-7100

55. *Justice, U.S. Department of

Anti-Trust Division

Washington, D. C. 20530

(301) 739-2385 _ r , ^

56. Kollmorgen Corp. ^

*a. Color Systems Division

67 Mechanic Street

Attlebora, Massachusetts 02703

(617) 222-3880

8a
F-16

*b. Macbeth Research Laboratories

Newburgh, New York 12550

(914) 561-7300

57. *Libbey-Owens-Ford Co.

Technical Center

1701 East Broadway

Toledo, Ohio 43605

(419) 242-5781

58. Lovibond

The Tintometer, Ltd.

Waterloo Road

Salisbury, Wilts

Great Britain

0722 27242

59. *Magnuson Engineers, Inc.

Instruments Division

1010 Timothy Drive

San Jose, California 95133

(408) 287-1260

60. Manufacturers Council on Color and Appearance

9416 Gamba Court

Vienna, Virginia 22180

(703) 938-4345

61. *Martin Sweets Co., Inc.

P.O. Box 1068

Louisville, Ky. 40201

(502) 774-5786

62. *McPherson Instrument Corp.

530 Main Street

Acton, Massachusetts 01720

(617) 263-7733

63. Merk Sharp and Dohme

West Point, Pa.

(215) 699-5311

64. Metro Litho-Graving Inc.

101 Moonachie Avenue

Moonachie, New Jersey 07074

(201) 935-1450

65. *Michaelson Laboratory

China Lake, California 93555

(714) 939-2869

66. *Michigan, University of

Infrared and Optics Laboratory

Ann Arbor, Michigan 48104

(313) 483-0500

81
F-17

67. *Mines, U.S. Bureau of

College Park Metallurgy Research Center

College Park, Maryland 20740

(301) 864-3100

68. ^Minnesota Mining and Manufacturing Co.

3M Center

St. Paul, Minnesota 55101

(612) 733-1374

69. Monsanto Company

Technical Liaison

1101 17th Street, N.W.

Washington, D. C. 20036

(202) 296-0050

70. '^Munsell Color Co., Inc.

2441 N. Calvert St.

Baltimore, Md. 21218

(301) 243-2171

71. ^National Broadcasting Co.

30 Rockefeller Plaza

New York, New York 10020 - ;

'

(212) 247-8300

72. National Oceanic and Environmental Administration

*a. National Environmental Satellite Center

Federal Office Building 4

Suitland, Maryland 20233

(301) 440-7114 .0'.

b. Coastal Mapping Division

(301) 146-8230 ...

73. ^National Research Council of Canada

Division of Physics

Ottowa 7, Ontario

Canada

(613) 993-2478

74. National Physics Laboratory

Metrology Centre

Teddington, Middlesex

England

01-977-3222

75. *Naval Electronics Laboratory Center

Infrared Technology Division

271 Catalina Blvd.

San Diego, Calif. 92152

(714) 226-6951

82
F-18

76. *Neotec Instruments, Inc.

6110 Executive Boulevard

Rockville, Maryland 20852

(301) 770-3525

77. *Newark Air Force Station

Infrared and Laser St ndards Laboratory

Newark, Ohio 43055

(614) 522-2171

78. Norris Paint and Varnish Co., Inc.

1675 Commercial Street, N.E.

Salem, Oregon 97308

(503) 364-2277

79. Oregon State University

Department of Oceanography

Corvallis, Oregon 97331

(503) 754-3504

80. Optical Coating Laboratory, Inc.

2789 Giffen Ave.

Santa Roas , Calif. 95403

(707) 545-6440

81. ^Optronics Laboratories, Inc.

7676 Fenton Street

Silver Spring, Md. 20910

(301) 587-2255

82. *0wens-Illinois Technical Center

1700 N. Westwood St.

Toledo, Ohio 43607

(419) 242-6543

83. Pharmaceutical Manufacturer's Association

1155 15th St. , N.W.

Washington, D. C. 20005

(202) 296-2440

84. *Photovolt Corporation

1115 Broadway

New York, N.Y. 10010

(212) 989-2900

85. Physikalisch-Technische Bundesanstalt

Abt. 4

D-3300 Braunschweig

Bundesallee 100

West Germany

86. The Proctor and Gamble Co.

Spring Grove and June St.

Cincinnati, Ohio 45217

(513) 562-1100

83
F-19

87. ^Radiant Color

2800 Radiant Avenue

Richmond, California 94804

(415) 233-9119

88. *Rensselaer Polytechnic Institute

Troy, New York 12181

(518) 270-6458

89 . *Rohin and Haas Company

P.O. Box 219

Bristol, Pennsylvania 19007

(215) 788-5501

90. Roland Robinson Associates

P.O. Box 132

Chantilly, Virginia 22021

(703) 471-7088

91. Sears Roebuck and Co.

Department D/817 •' - 3301 W. Arthington

Chicago, Illinois 60607 i C' ^

92. Sci Tech Corp.

301 West High St. • West Chester, Pennsylvania 19380

(215) 692-7861

93. *Sherwin-Williams Co.

101 Prospect Ave. ' ' Cleveland, Ohio 44115

(216) 566-2242

94. *Society of Motion Pictures and Television Engineers

9 East 41st St.

New York, N.Y. 10017 - (212) 867-5410 -

'

95. Spectral Data Corporation

Box 555 -o ^ -fi Hicksville, New York 11802

(516) 433-3910 '

96. Spectral Imaging, Inc.

572 Annursnac Hill Road ' ' - Mii.^v

Concord, Mass. 01742

(617) 259-8330 -

97. *Spex Industries, Inc.

3880 Park Ave.

Metuchen, New Jersey

(201) 549-7144

84
F-20

98. Spring Mills, Inc.

Fort Mill

South Carolina 29715

(803) 547-2901

99. Squibb Pharmaceuticals

P.O. Box 191

New Brunswick, N.J. 08903

(201) 545-1300

100. Swedish Forest Products Research LaboratoryBox 5604

S-11486 Stockholm

Sweden

101. *Technicolor , Inc.

6311 Romaine St.

Hollywood, Calif. 90038

(213) 462-6111

102. *Teledyne CAE

1510 Laskey Road

Toledo, Ohio 43601

(419) 475-4641

103. Toyo Rika Instruments Inc.

32 Banshu-Cho , Sinjuku-Ku

Tokyo, Japan

Phone Tokyo (341) 4191

104. *Transportation, U.S. Department of

Fairbanks Highway Research Station

ChainBridge and Great Falls Roads

McLean, Va.

Washington, D. C. 20591

(703) 557-5214

105. *G. K. Turner

2524 Pulgas Ave.

Palo Alto, Calif. 94303

(415) 324-0077

106. Willey Corp.

P.O. Box 670

Melbourne, Florida 32901

(305) 727-2076

107. Wright-Patterson Air Force Base

a. Target Signature Program

(515) 255-2759

b. Technology Division

c. Photographic Materials Lab.

Ohio 45433

85
F-21

108. Xerox Corp.

800 Phillips Road

Webster, New York 14580

(716) 872-2000

109. *Carl Zeiss, Inc.

444 Fifth Ave.

New York, N.Y. 10018

(212) 736-6070

86
F-22

C.3 LITERATURE REFERBJCES which are specifically cited in the text and

appendices of this report are Included In this list. The order in the list

Is the order of appearance in the report, and the text reference is given

as C.3 followed by the number of the item in the list below. For example,

the first reference would be Indicated in the text as (C.3.1).

1. Knock, Richard T. ; Long Range Planning Service Report #447,

Stanford Research Institute, Menlo Park, California; (October

1971); "Analytical Instruments".

2. Lorah, L. D. ; Mechanical Engineering, 27 (January 1972);

"Infrared Spectrophotometry: A Quality Control Tool" (Q.l).

3. Johnston, R. M. ; Journal of Paint Technology 39., 346 (1967);

"Spectrophotometry for the Analysis and Description of Color".

4. FED-STD 595 (3rd ed) January 1968 (Supplemented by MIL-STD 795

(Feb. 1962)) "Colors; (for) Ready-Mixed Paints".

5. Billmeyer, F. W. , and J. G. Davidson; Journal of Paint Technology

41 , 647 (1969); "A Research Spectrogoniophotometer"

.

6. Spengman, W. F. ; Paint and Varnish Production (August, 1970)

"Quinacridon Pigments".

7. Bartolo, H. F. ; SPE Journal 26, #3, 65 (March 1970) "Quinacridone

Pigments in Plastics".

8. Simon, F. T. ; Journal of Color and Appearance 2^, #4, 5 (1972);

"The Two-Mode Method for Measurement and Formulation with

Fluorescent Colorants".

9. Hoffman, Konrad ; The Journal of Color and Appearance 1^, #2,

16 (1971); "Chromatic Integrating Sphere Error in Tristimulus

Colorimeters"

.

10. Rand, R. N. ; Clinical Chemistry 839 (1969); "Practical

Spectrophotometric Standards".

11. Gourl ey , J. , Rib, H. T. , and Miles, R. D. ; Photographic Science

and Engineering 12 , 27 (1968) ; "Automatic Technique for Abstractin

Color Descriptions from Aerial Photography".

12. Kortiim, Gustav; Reflectance Spectroscopy , Springerverlag, New York

Inc. (1969).

13. Little, Angela C. ; Food Technology 22, 71 (1969); "Reflectance

Characteristics of Canned Tuna".

14. Maurer, Frank W. ; Glass Packer/Processor, 30 (June 1967);

"Flavor, Color, and Other Characteristics of Foods of the Future".

87
F-23

15. Smith, Ora, and Davis, C. 0.; Potato Chipper (November 1961);

"Prevention of Graying in Dehydrated Potato Products".

16. Birth, G. S. and Norris, K. H. ; USDA Technical Bulletin No. 1341

(September, 1965); "The Difference Meter for Measuring Interior

Quality of Foods and Pigments in Biological Tissues".

17. Demas, J. N. and Crosby, G. A.: J. Phys. Chem. 991 (1971);

"The Measurement of Quantum Yields, A Review."

18. NBS List of Publications, LP39 ; "Colorimetry and Spectrophotometry,

Publications by the Staff of the National Bureau of Standards,

January 1906 through June 1962".

19. A Study Prepared for the Subcommittee on Science, Research and

Development of the Committee on Science and Astronautics, U.S.

House of Representatives. Ninety-second Congress, First Session, p 178

(Sept. 8, 1971); "National Bureau of Standards, Review of Its Organization and Operations".

20. Saunders, James B. and Robert J. Bruening; Astronomical Journal

73 , 415 (1968) ;"A New Interferometer Test and its Application to the 84

Inch Reflecting Telescope at Kitt Peak National Observatory".

21. Eckerle, K. L. and R. W. P. McWhirter; The Physics of Fluids 9_ 81 (1966) ; "Departures from Local Thermal Equilibrium in a Magnetically Driven Shock Wave".

22. Berg, H. F. , K. L. Eckerle, R. W. Burris , and W. L. Wiese; The

Astrophysical Journal 139 , 751 (1964) ; "Relative Oscillator Strengths

of Some Oil and OIII Lines from Measurements on Shock-Heated Plasmas".

23. Roberts, J. R. and K. L. Eckerle; The Physical Review 153, 87 (1967);

"Measurements of Relative Oscillator Strengths of Some CII Multiplets".

24. Haupt, G. W. , J. C. Schleter, and K. L. Eckerle; NBS Technical Note 716

(1972) ; "The Ideal Lovibond Color System for CLE Standard Illuminants

A and C Shown in Three Colorimetric Systems".

25. Mielenz, K.D. and K. L. Eckerle; NBS Technical Note 729 (1972); "Design

Construction, and Testing of a New High Accuracy Spectrophotometer".

26. Mielenz, K. D. and K. L. Eckerle; Applied Optics 11, 2294 (1972);

"Spectrophotometer Linearity Testing Using the Double-Aperture Method".

27. Mielenz, K. D. , and K. L. Eckerle; Applied Optics 11, 594 (1972);

"Accuracy of Polarization Attenuators".

28. Hsia, J. J.; M.S. Thesis, Purdue University (1964); "The Reproducibility

of Mechanically and Electrolytically Prepared Surfaces".

29. Hsia, J. J. ; Ph.D. Dissertation, Purdue University (1968) ; "Experimental

Investigation on the Reflectivity of Al, Cu, Zn, and Ni and Its Comparison

with Theory".

88
F-24

30. Touloukian , Y. S. (Ed.); Thevmophysical Properties of High Temperature

Solid Materials^ MacMillan Co. (1967) (J. J. Hsia contributed sections

on thermal radiation properties and thermal conductivity to this work.)

31. Hsia, J. J. and D. P. DeWitt; Journal of the Optical Society of America,

59 , 449 (1969); "Infrared Reflectance of Metallic Elements".

32. Richmond, J. C. and J. J. Hsia; HTD-Vol. 3 Recent Developments in

Thermophysical Properties Research ASME (1971) ; "Thermal Radiation

Properties of Solids and Methods of Measurement".

33. Richmond, J. C. and J. J. Hsia; presentation at AIAA 6th Thermophysics

Specialists Conference, Tullahoma, Tennessee (26 April 1971); "A High

Resolution Bi-Directional Reflectometer".

34. Richmond, J. C. and J. J. Hsia; NBS Special Publication 260-38 (May 1972);

"Standard Reference Materials: Preparation and Calibration of Standards

of Spectral Specular Reflectance".

35. Venable, W. H. , Jr.; MS Thesis, University of Florida (1956); "The

Development of a Recording Gamma Radiation Spectrometer"; and

Nucleonics 15 (//7) , 84 (July 1957) ; "Simple Recording Gamma-Ray

Spectrometer"

.

36. Venable, W. H. , Jr. ; Ph.D Dissertation, University of Alabama (1962)

;

"A Disk Loaded Waveguide Design for a Submillimeter Radiation Generator".

37. Venable, W. H. , Jr.; The Review of Scientific Instruments 37, 1443

(1966) ; "Tunnel Diode Chronotron Circuit for Picosecond Range".

38. Venable, W. H. , Jr. and J. B. Shumaker, Jr.; Journal of Quantitative

Spectroscopy and Radiative Transfer 9^, 1215 (1969) ; "Observations of

Departures from Equilibrium in a Nitrogen Arc"

.

39. Venable, W. H. , Jr.; Applied Optics £, 609 (1970) ; "Effects Upon

Radiant Intensity Measurements Due to Scattering by Optical Elements".

40. Keegan, H. J., J. C. Schleter, and V. R. Weidner; Journal of the

Optical Society of America 51, 1470 (1961) ; "Ultraviolet Wavelength

Standard for Spectrophotometry".

41. Keegan, H. J., G. W. Cleek, J. C. Schleter, and V. R. Weidner;

Optical Society of America Spring Meeting, Jacksonville, Florida

(March 1963) ; "Absorption Spectra of the Lanthanide Series of

Rare-Earth Glasses".

42. Keegan, H. J., G. W. Cleek, J. C. Schleter, and V. R. Weidner;

Optical Society of America Fall Meeting, Chicago, Illinois (October

1963) ; "Further Progress Towards Development of a Single Filer

for the Wavelength Calibration of Spectrophotometers Between 0.25

and 2.6 Microns".

89
F-25

43. Keegan, H. J., J. C. Schleter and V. R. Weidner; Symposium on Thermal Radiation of Solids, San Francisco, California (March 1964);

"Effect of Surface Texture on Diffuse Spectral Reflectance. Diffuse

Spectral Reflectance of Metal Surfaces".

44. Gates, D. M. , H. J. Keegan, J. C. Schleter, and V. R. Weidner;

Applied Optics ^, 11 (1965) ; "Spectral Properties of Plants".

45. Keegan, H. J. and V. R. Weidner; Optical Society of America Fall

Meeting, Philadelphia, Pennsylvania (October 1965); "IR Spectral

Reflectance of Frost".

46. Keegan, H. J. and V. R. Weidner; Optical Society of American Spring

Meeting, Washington, D. C. (March 1966); "IR Spectral Reflectance

at Controlled Temperatures".

47. Keegan, H. J. and V. R. Weidner; Optical Society of America Fall

Meeting, San Francisco, California (October 1966); "IR Spectral

Reflectance of Black Materials".

48. Bennett, J.M. and E. J. Ashley; Optical Society of American Spring

Meeting, Tucson, Arizona (April 1971); "Calibration of Instruments

for Measuring Reflectance and Transmittance"

.

49. Clarke, F.J.J. ; National Physical Laboratory Report MC3020 (March,

3, 1971); "Calibration of a Set of Ceramic Colour Standards".

50. Robertson, A.R. ; Applied Optics 11^, 1936 (1972); "Effect of

Polarization on Reflectance Factor Measurements".

51. George, Dianne , and T. Limperis; Air Force Avionics Laboraoory

Technical Report AFAL-TR-65-331 , Vol. II (1965); "Sources of

Experimental Errors in Spectrophotometric Measurements".

52. Burke, R.W. , E. R. Deardorff and 0. Menis ; (Scheduled to be

published in Journal of Research, NBS , December 1972); "Liquid

Absorbance Standards".

53. Byrd , R.E. and P. H. Almand ; Electro-Optical Systems Design 4^, #6, 10 (June 1972); "Molded Plastic Optics are Coming".

54. Johnson, S.M. ; Electro-Optics System Design _4, #3, 20 (March 1972);

"Photomultiplier Tubes: Surviving the Rugged Life".

55. Olson, G. ; American Laboratory (February 1972); "Applications of an Optical Multichannel Analyzer".

56. Sakalys, V.R. ; American Laboratory, p. 15 (March 1972); "A

Programmable Calculator-Controlled Spectrophotometer Data Processing

System".

90
F-26

57. Lord, J.S.; United States Patent 3,646,331 (Feb 29, 1972);

"Automatic 100% Line Adjustment of Spectrophotometers"

58. NBS Special Publication 250 (yearly); "Calibration and Test

Services of the National Bureau of Standards"

59. NBS Letter Circular LC-1017 (January 1967); "Standards for

Checking the Calibration of Spectrophotometers"

60. Keegan, H.J., J. C. Schleter, and M. A. Belknap; Journal of the

Optical Society of America _54 , 69 (1964) ; "Recalibration of the

NBS Glass Standards of Spectral Transmittance"

61. NBS Special Publication 260 (periodic) ; "Catalog of Standard

Reference Materials"

62. Keegan, H.J. , J. C. Schleter, and D. B. Judd ; Journal of Research

NBS 66A , 203 (1962); "Glass Filters for Checking Performance of

Spectrophotometer-Integrator Systems of Color Measurements"

63. Billmeyer, F.W. , and M. Saltzman; Pvinaiples of Color Technology

,

Interscience Publishers, New York (1966).

64. Judd, D.B.; Color in Business^ Science^ and Industry ^ John Wiley

and Sons, Inc., New York (1952).

65. Wyszecki, G. and W. S. Stiles; Color Science, John Wiley and Sons,

Inc. , New York (1967)

.

66. Nimeroff, I.; NBS Monograph 104, (January 1968); "Colorimetry"

.

67. Nimeroff, I., editor; Precision Measurement and Calibration,

Selected NBS Papers on Coloirimetry , NBS Special Publication 300,

Vol. 9 (June 1972).

68. Seabright, C. A.; Ceramic Bulletin 49^, 269 (1970; "Metamerism in

Colored Glazes"

69. Commanday , S. ; Final Report, Project 01-327-11, Burlington Industries

Research Center, (February 1971); "Colorimetry of Fluorescent Dyes"

70. Nimeroff, I.; Journal of the Optical Society of America 43, 531

(1953) ; "Propagation of Errors in Spectrophotometric Colorimetry"

71. Nimeroff, I.; Color Engineering, p. 24 (March-April 1967); "The

Variability of Color Measurement"

72. Nickerson, D. and C. W. Jerome; Illuminating Engineering 60^, 262

(1965); "Color Rendering of Light Sources: CIE Method of Specification

and Its Application"

91
F-27

73. Judd, D.B.; Illuminating Engineering 62 , 593 (1967); "A Flattery

Index for Artificial Illuminants"

74. Hunter, R.S.; Journal of Research, NBS 18^, 19 (1937); "Methods of

Determining Gloss"

75. Hunter, R.S. and others; Tappi 54, 2073 (1971); "Specular Gloss of

Paper and Paperboard at 75 Degrees; Proposed Revision of T 480 ts-65

as a Standard"

76. Judd, D. B.; Applied Optics 6, 13 (1967); "Physiological Optics at

the National Bureau of Standards"

77. Federal Register 35 , 17308 (November 10, 1970); "85 . 124--Smoke

Measurement System"

78. Rich, R.B.; Cummins Technical Report, Document Number 5425

(May 19, 1972); "Calibration of Neutral Density Filters"

79. A report by the Council for Optical Radiation Measurements, an activity of Technical Committee 1.2, United States National

Committee, CIE (1972); "Pressing Problems and Projected National Needs

in Optical Radiation Measurements, A Consensus of Services Desired

of NBS"

80. Goebel, D.G., B. P. Caldwell, and H. K. Hammond III; Journal of the

Optical Society of America 5^, 783 (1966); "Use of an Auxiliary Sphere

with a Spectrophotometer to Obtain Absolute Reflectance"

81. Budde, W. and C. X. Dodd ; Die Farbe 19, 94 (1970; "Absolute

Reflectance Measurements in the D/0° Geometry"

82. Korte, H. and M. Schmidt; Lichttechnik 19, 135A (1967); "Uber

Messungen des Leuchtdichtefaktors an beliebig reflektierenden Proben"

83. Billmeyer, F.W. and J. G. Davidson; Journal of Paint Technology

41 , 647 (1969) ; "A Research Spectrogoniophotometer"

84. Yegerov, G.N. and Yu. M. Grigor'y^v; Svetnotechnika , No. 8,

p. 14-16 (August 1969); "Type GF-65 Goniophotometer"

85. Blair, M.E., D. C. Cramer and S. R. Stewart; Technical Report

AFAL-TR-70-161 , Air Force Avionics Laboratory, Air Force Systems

Command, WPAFB Ohio; "A Gonioreflectometer Facility Using Coherent

and Incoherent Sources"

86. Brandenberg, W. M. and J. T. Neu; Journal of the Optical Society of

America _56, 97 (1966) ; "Unidirectional Reflectance of Imperfectly

Diffuse Surfaces"

87. Turner, G.K. ; Science 146 , 183 (1964); "An Absolute Spectrofluorometer"

88. Turner, G. K. ; G. K. Turner Associates (C. 2 . 101) (1967) ; "Fluorometry

Principles, Techniques, Advantages, Applications"

92
F-28

89. Velapoldi, R.A. ; Conference on Accuracy in Spectrophotometry and

Luminescence Measurements, National Bureau of Standards (March 22-24,

1972) ; "Fluorescence Standards"

90. Simon, F.T.; The Journal of Color and Appearance 1_, //4 , 18 (1972);

"The Two-Mode Method for Measurement and Formulation with Fluorescent

Colorants"

91. Keegan, Harry J. and Gibson, Kasson S. ; Journal of the Optical Society

of America 3^, 770 (1944) ; "On the Use of Working Standards of Didymium

and Vitrolite Glasses for Spectrophotometric Measurement" (Abstract)

92. Keegan, Harry J.; Journal of the Optical Society of America 38_, 658

(1948) and Analytical Chemistry 20, 387 (1948) ; "Standards of

Reflectance" (Abstract)

93. An internal NBS document providing instructions for writing issue

studies for FY 74 (1972); "Issue Study Format and Schedule"

94. Department of Commerce, Bureau of the Census (1970); "Statistical

Abstract of the United States 2970"

95. Thiel, A. K. and C. D. Graves, paper presented to The Committee on Science and Astronautics, U.S. House of Representatives (January

25, 1972); "Remote Sensing of Earth Resources"

96. U.S. Bureau of Mines (1972); Minerals Yearbook^ 1970, Vol. 1

93

NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUMLIC ATION OR RI-IPORT NO. 2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

The National Measurement System for

Spectrophotometry

5. Publication Date November 1977

6. Performing Organization Code

7. AUTHOR(S)

William H. Venable, Jr.

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as No. 9

13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRAC T (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

A special study of the spectrophotometric measurement system was made in

order to determine what could be done to improve these measurements and what

benefits would result from the improvements. It was found that improvements

in the measurements could make large contributions to productivity, health,

and safety in the U.S., and that, because of the fragmented nature of this

measurement community, the improvements in spectrophotometric measurements

can be realized most efficiently through the efforts of a centralized agency

such as NBS. With the aid of this study, the program in spectrophotometry

at NBS has been revised in order to bring about these improvements more

rapidly and effectively

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Absorption spectra; automation; chemical analysis; colorimetry; heat transfer;

reflectance; remote sensing; retroreflectance; spectrophotometry; transmittance.

18. AVAILABILITY PC] Unlimited

[13! Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. CH

1 Xi Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

21. NO. OF PAGES

100

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price $6.00

USCOMM.DC 29042-P74