NATIONAL BUREAU OF STANDARDS REPORT

4343

Photometric Tests of 21 Colored Retroref lective Samples

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201-20-2301 4343

November 21, 1955

Photometric Tests of 21 Colored Retroref lective Samples

By

Photometry and Colorimetry Section

Optics and Metrology Division

S'

Project No. TED NBS AE- 10002

of the

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

Washington 25, D. C.

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, ri

unless permission I

25, D.C. Such pe

cal ly prepared If

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

‘ In part, is prohibited

tandards, Washington

eport has been specifieport for its own use,
I

I

I

•v
21 P-14/55

Report on

Photometric- Tests

of

21 Colored Retroref lective Samples

Tested for

Airborne Equipment Division

Bureau of Aeronautics

Department of the Navy

Washington 25 0 D. C.

1, SCOPE

This report gives the results of photometric tests made

on 21 samples of colored retroreflective devices or materials

produced by several manufacturers,.

These tests were requested by the Visual Landing Aids

Section 0 Bureau of Aeronautics, Navy Department, in letter Aer~

AE-l(KNo. 147711, dated 17 October 1952 as part of Project No.

ted NBS AE- 10002

o

2» INTRODUCTION

A discussion of the types of retroreflectors and terms used

in discussing them is given in NBS Report 3789, Photometric Tests

of 36 Retroreflective Samples, dated November 10, 1954.

In all types of colored retroreflectors, the colored light

returned to the observer is the result of selective absorption by

a colorant. This colorant may be used either in the material of

which the reflector is made or as a coating of the entrance surface. Retroreflectors made with both methods of coloration were

used in this test. The concentration of the colorant, used will,

of course, be determined by the length of the path through the

colored media.

3. MATERIAL TESTED

The reflectors tested are listed in table I. The Stimsonite

reflectors are of the trihedron mosaic plaque type; both red and

green reflectors were tested. The Scotchlite reflective material

is made of beads in plastic; red, yellow, and green samples were
II
tested. The Reflexite reflectors are of the embossed lens type;

red, amber, blue, and green samples were tested. The Cataphote

reflectors are individual units of the ’’cat” s-eye" type; both

red and green reflectors were tested.

Samples designated by an asterisk (*) were supplied by the

Coast Guard. The remainder of the samples had been sent previously to the National Bureau of Standards by the manufacturers.

4. TEST PROCEDURE

All measurements were made by the method described in NBS

Report 3789 with two modifications.

Since the comparison lamp radiated "white” light and the light

returned from the reflectors was colored, it was necessary to use colored filters in front of the comparison lamp. For each retroreflector an approximate visual color match was made by selecting

a suitable filter. It was then necessary for the comparison lamp

to be calibrated for each filter used. Instead of varying the

intensity of the source light, and hence its color temperature,

in order to maintain a predetermined illumination on the test

sample, the source light was operated at a color temperature of

2854 °K, and the illuminance at the sample measured. Since the

retroreflectors were illuminated by "white” light, it was unnecessary to modify the illuminometer which was used to measure the

illuminance at the retroreflectors.

4.1 Choice of Angles Used

The test request asked for measurements for incidence angles

varying from normal incidence to the incidence angle at which the

specific intensity falls to one-tenth that at normal incidence and

for divergence angles of 0°, 0.5°, and 1°. These angles were used.

Additional angles were used for a few samples.

5. TEST RESULTS

The results of these tests are given in tables II to V. In

each table the results of the tests of the retroreflectors of one manufacturer are given. Values of specific intensity are given for

the retroreflectors of unit (fixed-area) construction only. Values

of specific intensity per unit area and luminance factor are given

for all samples.
'
=3=

In these tables,, the entry of a dash instead of a numerical

entry indicates that the specific intensity of the sample, under

these conditions of illumination and view, was too low to permit

measurement. No entry indicates that no observation was made at

this point.

Figure 1 consists of broken-line graphs of several representative red samples of different manufacturers showing the variation

in specific intensity per unit area with change of angle of incidence at 0° divergence. Figure 2 is a similar set of graphs for

green samples. The performance graphs of all the types of colored

retroreflectors made by one manufacturer and used in this test

are shown in a similar manner on a single figure. These figures

are

Stimsonite

Scotchlite

Reflexite

Cataphote

figure 3

figure 4

figure 5

figure 6

For convenience in comparing the performance of colored retroreflectors with that of colorless retroreflectors, graphs for

representative colorless samples have been included on figures 4 e 5, and 6. Graphs for colorless Stimsonite retroreflectors have

not been included since an adequate presentation of the colorless

samples on the same graph with colored samples would have required

a change in scale. This change in scale would make intercomparison

of colored samples of different manufacturers more difficult and

would introduce possible confusion. Performance data of colorless

Stimsonite retroreflectors are given on figures 5 and 6 of NBS

Report 3789,

6. DISCUSSION

It would be highly desirable if it were possible to determine

the performance of a colored retroreflector by measuring its intensity at only one point (say at incidence and divergence angles

of 0°) and using the ratio between this intensity and the intensity

of a similar colorless retroreflector at the same point to obtain

the performance graphs of the colored retroreflector from those

of the colorless retroreflector. In NBS Report 3789 it was noted

that reflectors of the same type and manufacturer very frequently

have widely differing characteristics, A study of the shapes of

the performance graphs of colored retroreflectors and those of clear

retroreflectors of the same type shows general similarity. However,
I . 1Ilc
4-

since the data in NBS Report 3789 was obtained with a limited num- ber of samples and the data in this report was obtained from one sample of each type, it does not appear that the use of this ratio

is justifiable at this time. If a sufficient number of each type

of colorless retroreflectors were measured to result in a statistically good mean performance graph, it might prove satisfactory

to use the single point measurement of a number of colored re- flectors to obtain a mean performance curve for the colored retroreflectors.

Another possible method of obtaining the performance of a ""typical 1’'’ colored retroref lector is to determine the spectral

transmittance of a sample of the colored material of the retroreflector and to compute the transmittance of a sample of thickness

equal to the length of the average light path in the colored part

of the retroreflector. (Note that the length of the light path in

a lens-reflector type of retroreflector is very nearly equal to

twice the thickness of the colored material whether it is ^ colored

sheet or film over or under the lenses or is in the lens itself.

The length of the light path in a trihedral type of retroreflector

formed of colored material is very nearly equal to twice the distance from the front surface to the apex of an element of the

reflector.) Then, the specific intensity at a given point of a "typical 50 colored reflector is obtained from the product of the

transmittance and the specific intensity of the "typical" colorless

reflector at that point,.

Table I

List of Retroref lectors Tested

Material Tested ;urer ;ion Marks

STIMSONITE No, 19, Red Stimsonite Plant AGA CG*5*

Div. , Elastic Stop Nut

Corp, of America,

Chicago, Illinois

STIMSONITE No, 12, Red CG*9*

STIMSONITE No, 10, Red CG*10*

STIMSONITE No, 19, Green CG*6*

STIMSONITE No, 12, Green CG*7*

STIMSONITE No, 10, Green CG*8*

SCOTCHLITE, Standard, Scotchlite Reflective

Flame Red *232 Products Div, , Minnesota

Mining & Manufacturing

Co,, St, Paul, Minnesota

SCOTCHLITE "Flat-Top",

Red *2252

SCOTCHLITE, Wide Angle,

"Flat- Top”, Red *2272

SCOTCHLITE "Flat-Top",

Green *2257

SCOTCHLITE, Wide Angle,

"Flat-Top", Yellow *2271

REFLEXITE, R69R, Red Reflexite Corporation

New Canaan, Conn,

REFLEXITE, R56R, Red
r!!*'?'PPI[I
• 6-

Table I (continued)

Material Tested Manufacturer Identification Marks

REFLEX I TE, G69R, Green

REFLEXI TE, G55R, Green

REFLEXITE, A69R, Amber

REFLEXITE, A59R, Amber

REFLEXITE, B69R, Blue

REFLEXI TE, B56R, Blue

CATAPHOTE, *1A, Red Cataphote Corporation, #1A Red*

Toledo, Ohio

CATAPHOTE, # 1A, Green tt lA Green*

* Samples supplied by Coast Guard

- 1 - I

Table II

Retroreflectors Manufactured by Stimsonite Plant,

AGA Division of Elastic Stop Nut Corporation of America

a. Specific Intensity

Angle of Angle of Divergence

Incidence 0° o 1°

Style *19 - Red

0°

(4 3/4*' diameter)

15

- (CG*5)

2.9 0.24

-10° 15 2.4 0.23

-20° 4 0 5 0.87 0. 18

-30° 2 0 2 0.87 0.15

-40° 0.76 0.38 0.084

-50° 0.15 0.098 0.056

-60° 0.056 __

Style *12 - Red (2 3/4” diameter) -- (CG*9)

0° 10. 3.7 0.64

-10° 7.b 3.4 0.50

-20° 3.9 1.7 0.39

-30° 1.6 1.1 0.31

-40° 0.66 0.47 0. 14

Style *10 - Red (1 1/2” diameter) - (CG* 10)

0° 1.1 1.5 0.27

-10° 0.97 0.92 0.17

-20° 0.54 0.59 0.067

-30° 0.31 0.21 0.037

-40° 0.20 0.090 0.032
!
-2 -

Table II (continued)

a. Specific Intensity (continued)

Angle of

Incidence

Anale of Diveraence

0° 1/2° 1°

Style *19 - Green (4 3/4" <diameter) - (CG*6)

0° 63 13 1.6

-10° 44 7.1 1.5

-20° 16 1.1

-30° 9.0 2.4 0.46

-40° 1.7 1.1 0.30

-50° 0.19 0.15 0.062

-60° 0.14 0.084 0.040

Style *12 - Green (2 3/4" diameter) - (CG*7)

0° 13 2.7 0.48

-10° 11 1.8 0.34

-20° 3.8 1.4 0.32

-30° 1.0 0.53 0.17

-40° 0.44 0.28 0.11

Style *10 - Green (1 1/2" diameter) - (CG*8)

0° 2.4 1.2 0.46

-10° 1.8 0.88 0.46

-20° 1.0 0. 55 0.21

-30° 0.42 0.30 0.16

-40° 0.26 0.16 0.054

-50° c=»
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% Table II (continued)

b. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° 1/2° 1°

Style *19 - Red (CG*5)

0° 0.870 0.17 0.014

=10° 0.870 0.14 0.013

-20° 0.26 0.051 0.010

-30° 0.13 0.051 0.085

=40° 0.044 0.022 0.0049

-50° 0.0089 0,0057 0.0032

“60° 0.0032 “

Style *12 - Red (CG*9)

0° 1.6 0.62 0.11

-10° 1.3 0.55 0.082

-20° 0.64 0.29 0.064

-30° 0.27 0.18 0.051

-40° 0.11 0.078 0.024

Style *10 - Red (CG*10)

0° 0.77 1.0 0.18

-10° 0.66 0.62 0.12

-20° 0.37 0.40 0.046

=30° 0.21 0.14 0.025

-40° 0.14 0.061 0.022

Style *19 - Green (CG*6)

0° 3.6 0.76 0.095

=10° 2.6 0.41 0.089

-20° 0.93 0.062

=30° 0.52 0.14 0.027

-40° 0.10 0.062 0.017

-50° 0.011 0.0088 0.0036

-60° 0.0079 0.0049 0.0023
.
Table II (continued)

b. Specific Intensity per Square Inch (continued)

Angle of

Incidence

. Anole of Divergence

0° 1/2° 1°

Style *12 - Green (CG*7)

0° 2.2 0.45 0.080

-10° 1.9 0.30 0.057

-20° 0.63 0.22 0.052

-30° 0. 17 0.087 0.029

-40° 0.072 0.047 0.018

Style *10 - Green (CG*8)

0° 1.6 0.79 0.31

=10° 1.3 0.60 0.31

-20° 0o 68 0.37 0.14

-30° 0.29 0.21 0.11

-40° 0.18 0.11 0.037

-50° «=

c. Luminance Factor

Style *19 - Red (CG*5)

0° 400 75 6.4

-10° 410 67 6.3

“20° 140 26 5.2

“30° 79 31 5.2

-40° 34 17 3.8

=50° 9.8 6.3 3.6

-60° 5.8 «=» *

Style *12 - Red (CG*9)

0° 750 280 48

-10° 600 260 39

-20° 330 148 33

=30° 160 110 31

-40° 84 61 19
f
-5-

c. Lurainc

Angle of

Incidence

Table II (continued)

mce Factor (continued)

Angle of Divergence

0° . 1/2 ° 1°

Style *10 - Red (CG*10)

0° 350 470 83

-10° 310 290 55

-20° 190 210 24

-30° 130 87 16

-40° 110 48 17

Style *19 - Green (CG*6)

0° 1700 350 43

-10° 1200 190 42

-20° 480 32

-30° 320 85 16

-40° 77 49 14

>50° 12 9©8 4.0

=60° 14 9© 0 4.4

Style *12 - Green (CG*7)

0° 1000 200 36

-10° 880 140 27

-20° 330 120 27

-30° 100 53 18

-40° 56 36 14

Style *10 = Green (CG*8)

0° 730 360 140

-10° 590 280 150

-20° 350 190 75

-30° 170 130 69

-40° 140 87 29

-50° — »

-1 - m

Table III

Retroreflectors Manufactured by Scotchlite Reflective

Products Division of Minnesota Mining and Manufacturing Co.

a. Specii

Angle of

Incidence

.ic Intensity per Square Inch

Anole of Diveraence 0° 1/2° 1°

Standard, Flame Red *232

0° 0.27 0.10 0.064

-10° 0.08 0.037 0.029

-20° 0.018 0.0092 0.0047

-30° «=> *=* ®*

"Flat-Top” Red *2252

0° 0.087 0.048 0.033

-10° 0.069 0.038 0.031

-20° 0.041 0.030 0.021

-30° 0.013 0.0095 0.0079

Wide Angle "Flat-Top", Red *2272

0° 0.21 0.11 0.062

-10° 0.12 0.057 0.039

-20° 0.097 0.055 0.026

-30° 0.060 0.039 0.018

-40° 0.032 0.019 0.0089

-50° 0.012 0.0068 0.0039

"Flat-Top", Green *2257

0° 0.28 0.12 0.061

-10° 0.15 0.084 0.040

-20° 0.044 0.027 0.020

=30° 0. 0074 0.0033 -

-2

Table III (continued)

a. Specific Intensity per Square Inch (continued)

Angle of

Incidence

Anale of Di¥eraence

0° i h° 1°

Wide Angle "Flat-Top", Yellow *2271

0° 0.45 0.20 0.088

-10° 0.29 0.17 0.088

-20° 0.32 0.12 0.088

-30° 0.18 0.13 0.053

-40° 0.058 0.043 0.022

-50° 0.019 0.011 0.008

b. Luminance Factor

Standard, Flame Red *232

0

° - 10 ° 120 45

40 18

9.0 4.8

29

14

2.4

"Flat-Top”, Red *2252

0° 40 22 15

-10° 32 18 15

-20° 21 15 11

-30° 8.0 5.8 4

Wide Angle "Flat-Top”, Red *2272

0° 96 51 28

-10° 58 27 18

-20° 50 28 13

-30° 37 24 11

-40° 25 15 7.0

-50° 13 7.6 4.4

-3-

Table III (continued)

b. Luminance Factor (continued)

Angle of Angle of Divergence

Incidence £2 L(21 LI

"Flat-Top", Green *2257

0° 130 53 28

-10° 70 39 19

-20° 22 14 10

-30° 4.5 2.0

Wide Angle "Flat-Top", Yellow *2271

0° 200 91 40

-10° 140 80 41

-20° 160 60 46

-30° 110 79 32

-40° 45 34 17

-50° 21 12 9,

-1 -

Table IV

Retroreflectors Manufactured by

Reflexite Corporation

a. Specific Intensity per Square Inch

Angle of Angle of Divergence

Incidence 0° 1/2° 1°

R69R - Red

0° 0.49 0.098 0.024

=10° 0.30 0.053 0.0099

-20° 0.11 0.021 0.0097

=30° 0.0062 ““

R56R - Red

0° 0.038 0.020 0.015

-10° 0.019 0.012 0.010

-20° 0.019 0.0058

-30° 0.013 0,0078 .—

.

G69R - Green

0° 0.70 0.075 0.018

=10° 0.68 0.036 0.0061

-20° 0.029 0.017 0.0010

-30° 0.015 0.0088 -= -40° 0.015

(D «3 C3 C3 <D

G55R - Green

0° 0.028 0.017 0.011

-10° 0.020 0.011 0.0083

-20° 0.017

-30° 0.0098 ——

-2 - #

Table IV (continued)

a. Specific

Angle of

Incidence

Intensity per Square Inch (continued)

Angle of Divergence

0° 1/2° 1°

A69R - Amber

0° 0.94 0.24 0.083

-10° 0.64 0.12 0.027

-20° 0.10 0.046 0.015

-30° 0.015 0.0070 0.0038

A59R - Amber

0° 0.14 0.090 0.063

-10° 0.16 0.063 0.036

“20° 0.13 0.042 0.0095

-30° 0.019 0.0074 0.0026

B69R - Blue

0° 0.30 0.037 0.010

-10° 0.15 0.025

=20° 0.017 0.0094

-430° 0.0092 __ --

B56R - Blue

0° 0.012 0.0090 0.0083

-10° 0.0094 0.0064 0.0043

-20° 0.0076 0.0037

Table IV (continued)

b. Luminance

Angle of

Incidence

Factor

Anale of Diveraence

0° 1/2° 1°

R69R - Red

0° 220 44 11

=10° 140 25 4.6

-20° 56 11 5.0

-30° 3.8

R56R - Red

0° 17 8.9 6.8

-10° 8.8 5.7 4.8

-20° 9.7 3.0 - -30° 8.1 4.8 —

G69R - Green

0° 320 34 8.0

-10° 320 17 2.8

-20° 15 8.6 0.53

-30° 8.9 5.4

-40° 11 —

G55R - Green

0° 12 7.8 5.1

-10° 9.4 5.3 3.9

-20° 8.8 — -30° 5.9 - —

A69R - Amber

0° 430 no 38

-10° 300 58 13

-20° 53 24 7.8

-30° 9.1 4.3 2.3

Table IV (continued)

b. Luminance Factor (continued)

Angle of

Incidence

Anale of Diveraence

0° 1/2° 1°

A59R - Amber

0° 65 41 29

-10° 74 30 17

-20° 66 22 4.9

-30° 12 4o5 1.6

B69R = Blue

0° 140 17 4.5

-10° 70 12 «. -20° 9.0 4.8 => =30° 5.6

B56R = Blue

0° 5.4 4.1 3.8

-10° 4.4 3.0 2.0

=20° 3.9 1.9

Table V

Retroreflectors Manufactured by

Cataphote Corporation

a. Specific Intensity

Angle of

Incidence

Anale of Diveraence

0° 1/2° 1

° ...

#1A Red (3/4’' diameter)

0° 0.31 0.17 0.053

-10° 0.31 0.14 0.060

-20° 0.19 0.20 0.14

=30° 0.043 0.034 0.023

-40° — —

tf lA Green (3/4" diameter)

0° 1.9 0.70 0.20

-10° 1.5 0.72 0,31

-20° 0.44 0.33 0.37

-30° 0.13 0.11 0.12

-40° 0. 0094 —

b. Specific Intensity per Square Inch

# 1A Red

0° 0.70 0.39 0.12

-10° 0.70 0.31 0.14

-20° 0.44 0,45 0.31

-30° 0.097 0,078 0.052

-40° “ ** **

ff lA Green

0° 4.2 1,6 0,44 -10° 3.3 1.6 0,69

-20° 0.96 0,73 0,83 -30° 0.29 0,25 0,28

-40° 0,021 — —

e„ Luminance Factor

-2 =

Table V (continued)

Angle of Angle of Divergence

Jnc.i de.P£& 1/2.°. Li

^1A Red

0° 320 180 55

-10° 330 150 64

-20° 220 230 160

=30° 59 47 32

=40°

tt lA Green

0° 1900 700 200

-10° 1500 750 330

=20° 500 380 430

-30° 170 150 170

-40° 16 -«=» ==

S PECIFIC INTENSITY

-AS- A- FUNCTION OF ANGLER- INCIDENCE—

-at -^Divergence

_ Representative

Redj Retroref lectors

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*—Stimsonit© No. 19 f Red

© Scotehlite, Wide Angle

Flat^Tdp Red *2272

Beflexite, Type R< X Cataphc te No. 1A* Red

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NBS TEST 2 IP- 14/^5 -

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i !flI i I
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: The Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.