.J

N'BS

Pubfi - cations

A111D3 0^1733

. DEPARTMENT OF COMMERCE

nONAL BUREAU OF STANDARDS

i; SPECIAL PUBLICATION 480-23

Law Enforcement

Equipment Technology

Selection and Application

Guide to

POLICE

PHOTOGRAPHIC

EQUIPMENT
ACKNOWLEDGMENTS

This guide was prepared by the Law

Enforcement Standards Laboratory of the National Bureau of Standards under

the direction of Lawrence K. Eliason, Manager, Security Systems Program,

and Jacob J. Diamond, Chief of LESL.

Its preparation was sponsored by the

National Institute of Law Enforcement and Criminal Justice, Lester D. Shubin, Standards Program Manager.
OCT 10 1980

Selection and Application Guide to

POLICE PHOTOGRAPHIC EQUIPMENT

Prepared by

CHARLES C. GROVER

Naval Surface Weapons Center

Silver Spring. Md. 20910

and the

Law Enforcement Standards Laboratory Center for Consumer Product Technology

National Bureau of Standards

Washington, D C. 20234

Prepared for

National Institute of Law Enforcement

and Criminal Justice Law Enforcement Assistance Administration Department of Justice Washington, D.C. 20531

U.S. DEPARTMENT OF COMMERCE

Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary Jordan J. Baruch, Assistant Secretary for Productivity, Technology and Innovation NATIONAL BUREAU OF STANDARDS

Ernest Ambler, Director
The use of trade names or company products in this guide does not constitute endorsement or recommendation by the National Bureau of

Standards and does not imply that the products

are necessarily the best available for the purpose.

Library of Congress Catalog Card Number: 80-600109

National Bureau of Standards

Special Publication 480-23

Nat. Bur. Stand. (U.S.), Spec. Publ. 480-23, 65 pages CODEN:XNBSAV

U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1980

For sale by the Superintendent of Documents,

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5^ U.S. GOVERNMENT PRINTING OFFICE : 1980 O—31 1-065 (134)
CONTENTS

Foreword v

Introduction vi

Typical Photographic Assignments 1

Cameras 9

Lenses 25

Exposure Meters 39

Film 43

Lighting Equipment 51

Filters and Other Accessories 57

FOREWORD

The Law Enforcement Standards Laboratory (LESL) of the National Bureau of Standards (NBS)

furnishes technical support to the National Institute of Law Enforcement and Criminal Justice

(NILECJ) program to strengthen law enforcement and criminal justice in the United States. LESL's function is to conduct research that will assist law enforcement and criminal justice

agencies in the selection and procurement of quality equipment.

LESL is: (1) Subjecting existing equipment to laboratory testing and evaluation and (2) conducting research leading to the development of several series of documents, including

national voluntary equipment standards, user guides, and technical reports.

This document is a law enforcement equipment guide developed by LESL under the

sponsorship of NILECJ. Additional guides as well as other documents are being issued under

the LESL program in the areas of protective equipment, communications equipment, security

systems, weapons, emergency equipment, investigative aids, vehicles and clothing.

Technical comments and suggestions concerning this guide are invited from all interested

parties. They may be addressed to the author or to the Law Enforcement Standards Laboratory,

National Bureau of Standards, Washington, D.C. 20234.

Jacob J. Diamond

Chief, Law Enforcement Standards Laboratory
INTRODUCTION

Virtually every segment of the law enforcement

community makes extensive use of photography on a daily basis, preparing documentation, evi- dence, or visual aids for training and public

education. Law enforcement photography, as a

specialty, probably encompasses a broader

range of specialized photographic skills than

any other recognized branch of the photographic profession. This guide briefly discusses the

typical assignments that are encountered on a

routine basis and reviews the types of pictures

that the photographer must obtain in each

instance. Those problems that are unique to specific assignments are identified, and some

useful photographic techniques are described.

Cameras, lenses, film, exposure meters, lighting

equipment, and accessories are also discussed,

with emphasis on the characteristics that are important to law enforcement applications.

The upsurge in popularity of photography

among the general public has resulted in a flood

of new equipment, particularly in the 35 mm

field. The professional photographer has

benefited greatly from the availability of this sophisticated equipment. On the other hand, the

demand for specialized law enforcement equipment is relatively small, and some of the

popularly advertised equipment is not suitable

for law enforcement use. The individual making

the selection must choose from the large variety

which is commercially available. The final choice is often a compromise.

The purpose of this guide is to assist those law

enforcement and procurement officials who are

not technically trained in photography in the selection and application of photographic equipment which will meet their needs. The basic

operating principles of cameras, lenses and

other equipment are described in order to make

it easier to discuss the considerations which

affect their application to different photographic

assignments. Emphasis is placed upon picture

quality, acquisition and operating costs, and

equipment reliability, factors that must all be

taken into account when selecting equipment.

Matching equipment characteristics to specific

assignments will help in the selection of the

type that will produce the highest picture quality.

Judgment will have to be exercised and compromises may have to be made, based upon the rel- ative frequency of use of each type of equipment, personnel skills, and personal preference.

Only the individual who knows the requirements

of the user can judge these points properly.

In a field such as law enforcement photography,

where widely diverse subjects are normal, the

skill of the individual photographer is of maximum importance, and equipment cannot be substituted for professional competency. The

greatest portion of the annual cost of photographic services goes for labor rather than for equipment or materials. It would be sheer folly, therefore, to handicap the photographer by

forcing him to use inferior equipment which

wastes his time and talent. It is hoped that this guide will assist in the logical selection of photographic equipment which is best suited to the

job to be done.

The major manufacturers maintain technical

staffs to answer questions and assist in the application of their products to specific uses. They

have published a number of handbooks,

manuals, and technical bulletins that discuss

specific law enforcement applications, such as

forensic and evidential photography, in depth. In addition, the monthly photographic magazines

contain a great variety of photographic information and can enable a police department to become aware of new products as they are

introduced. The importance of keeping current

with photographic technology cannot be over emphasized. A month never goes by without the

introduction of a new camera, film, or accessory; which may often be ideally suited to law enforcement application.
TYPICAL

PHOTOGRAPHIC

ASSIGNMENTS

Basic law enforcement photographic

assignments are traditionally classified according to the crime or the object

photographed: homicide, burglary, breath- ing and entering, arson, sex crimes, etc.; mug shots, fingerprints, physical evidence,

documents, etc.
TYPICAL PHOTOGRAPHIC ASSIGNMENTS

Crime Scene and Physical Evidence

Photography

Photographs taken at the scene of a crime are

essential to the investigation and for later prosecution of those charged with the offense. The

purpose of crime scene pictures is to show in detail the objects, conditions, and relations

present at the time the investigating officers

arrived.

The normal crime scene assignment involves a number of different pictures with widely different

requirements. Overall views are needed to positively identify the location, showing the

general and immediate surroundings and their relations to the crime scene. Close-up pictures

must be taken at progressively decreasing

distances and from different views. The general

photographic sequence might go from street scenes to the dwelling, to the entry, to the room, the overall conditions of the room, and to any victim involved. Crime scene photography,

in general, involves relatively large areas and

the pictures must have good detail and perspective. Many of the pictures can be taken with

existing light; however, interior photography will most often require additional light. Another type

of crime scene photography is the recording of a re-enactment of a crime. This requires a somewhat different approach. The pictures

should be relatable and compatible with those

taken at the time of the initial investigation of the crime.

With the exception of those pictures taken to fix the location of the investigation, all pictures

made at the scene of a crime are potentially evi- dence photographs. It is particularly important

to obtain photographs of evidence that may be

transitory in nature, such as footprints, tire marks, or fingerprints.

When investigating a burglary or breaking and

entering, the pictures should include evidence

of the point of entry, tool marks, trace evidence

such as cigarette butts, articles left at the scene

such as tools, the condition of various rooms

and areas from which articles were taken, fingerprints or footprints and the articles or area where found, and the known or possible paths

of exit.

Photographs taken at the scene of a crime in- volving a victim, including drowning, are often

critical to determining whether the investigation concerns homicide, an accident, or suicide.

Pictures must be taken from all sides of the

body, and all wounds must be shown in detail. Any weapons present must also be photo-
graphed in detail. Coverage must be sufficiently

thorough to leave no possibility for later requirements which were not anticipated at the time.

After a full set of pictures has been made of the

victim as found, it will often be necessary to take additional pictures of the body, wounds,

blood stains under the body, or other additional

evidence once the body has been moved. As

with an investigation of breaking and entering,

points of entry and exit are important.

The photographic conditions encountered in crime scene assignments involve a wide range,

from large exterior objects under good illumination (such as a broken store window) to very

small objects under poor Illumination and in inaccessible locations (such as a bullet hole, at the scene of a shooting).

In many instances, the crime scene photograph

will be the only record of physical evidence for

later use, such as damage to a large wall safe

that cannot be removed from the property; in other cases, it will be possible to take items to the laboratory for further examination and photography. Weapons and tools can be studied

and photographed to display fingerprints, or unique characteristics that will aid in the investi-
gation. Items can be examined and photographed under other types of illumination such

as infrared or ultraviolet light, which may enable

the detection of such things as the alteration of an original check signature. The photography

studio will also be used to make records of property, such as a stolen radio picked up

during a pawn shop investigation.

Photographs of sex crime victims are still another type of evidential photography, and

require the full cooperation of the victim. Pictures may be necessary to substantiate the

fact that sexual assault was committed.

Evidence of resistance to the attack in the form

of wounds, bruises, scratches, etc., are of special importance.

Traffic accident pictures form a complete documentation of an automobile accident involving a

traffic fatality or injury. General views are

required to show the scene and to identify the

locality. It will be necessary to show as nearly as possible each driver's view of his surroundings prior to the accident, particularly his possible view of the approach of the other

vehicle; what view each driver had of the other

at the point of impact; general views of the

vehicles involved in relation to their surroundings; a close-up of the damaged vehicles, and

the locations of those injured or killed; views of

dirt dislodged from the underside of vehicles, in- dicating location of collision; views of tire or skid

marks or other evidence of preventive measures or lack of them. Any record that would indicate a mechanical failure of either

vehicle is also important.

Tire or skid marks require two views: one

looking in the direction of travel from as high an
I elevation as feasible, to indicate evasive maneuvers made by the driver; the second view

I at right angles to the direction of travel,

I enabling the length of the tire marks to be

determined. Such marks must also be

I measured.

j Arson photography represents one of the more

difficult assignments. It requires careful coverage from several viewpoints, which are not compatible. An overall general view of the scene of the fire, showing smoke formation,

' color of smoke and flame, location of initial flames and direction and speed of spreading is important. At the same time, pictures of the

' crowd of spectators should be obtained for the

possible identification of arson "repeaters" who

may be present. The first set of pictures can

best be taken from a considerable distance,

choosing the camera viewpoint carefully to show what is wanted. A long focus or telephoto

lens should be used. Crowd views require

working in close, at the scene of the action,

making it a difficult job for one person to cover.

After the fire, a complete record of the point

where the fire started, its direction of travel, the

damage, and any evidence of items that were

used in starting or spreading the flames must be

obtained. The required photographic techniques

are familiar to the experienced photographer. In the photography of fire-blackened areas, both

lighting and exposure must be modified to meet

the conditions found. Normal exposure, using

flat lighting of fire-blackened walls, produces

very poor picture quality. Lighting to emphasize

the texture of the burned surfaces should be
used. Exposure should be increased as required

to get black objects dense enough on the negative to provide good detailed reproduction.

Evidence of multiple starting points should be

photographed in any fire; this is often a sign of arson. In all cases, evidence should be photographed from a distance great enough to show

its relation to the surroundings, as well as close

enough to show the details.

7302^0 73asio

Identification Photographs

Identification or "mug" shots are an important

part of any criminal file. They are the only

method of reliably showing facial characteristics, and a good one will enable an investigator or witness to recognize a suspect on sight. At

least two views of each subject are required for an identification series to be complete: a front view and a side view. The identification photograph is most often a close-up of the head and

shoulders, extending down to the chest only far enough to show the identification or file number.

The side view is most important for absolute

identification; it provides many more elements

for positive identification than any other view.

To the untrained eye, however, the front view is more recognizable; it is widely used for display

to witnesses. Some police departments also

photograph a full length front view of the

standing suspect and occasionally a threequarter view from each side. In all cases, the

pictures should be lighted for maximum detail. The picture should include any unique features,

such as scars, birthmarks, etc., that would aid in

identification. Black and white pictures are more common, but color shots are being increasingly

used.

Identification photos traditionally have been

made in pairs on a 12.5 x 18 cm (5 x 7 in) negative, producing two 9 x 12.5 cm (3 1/2x5 in) prints, and there is a tendency to standardize on prints of about this size. Some special identi- fication cameras put three shots on a single

10 X 12.5 cm (4 x 5 in) negative, although two

is more common.

"Mug" shots are essentially portraits and the

same rules of good perspective govern. Use a

long enough focal length that it is not necessary

to bring the camera too close to the subject.

Fingerprints

Fingerprint photography is a specialty, and the

fingerprint expert will have a special set of techniques. The general law enforcement photographer will have more limited contact with fingerprints: prints found at the scene of a crime that must be photographed immediately, and photographs of lifted prints that are being prepared

for presentation to a hearing or court.

Fingerprints are made visible by four major

methods: (a) dusting with various colored

powders that stick to the prints, increasing their contrast against the surfaces on which they are

found; (b) "lifting" the powdered prints with an

adhesive-backed plastic tape and transferring

them to a more suitable background; (c) illuminating the prints with ultraviolet light to make them

fluoresce; (d) fuming the prints with chemical

vapors, such as iodine.

Fingerprints may be photographed with (a) a

special fingerprint camera, which is a self- contained unit providing fixed magnification and

integral lighting; (b) with a press-type camera

adapted for fingerprint photography by means

of special attachments; or (c) with any other

type of camera which is suitable for close-up

photography.

In printing fingerprints for court presentation,

they should always be printed so that the ridges are dark and the grooves are light. This may
necessitate printing from a positive transparenj cy made from the negative, instead of directly

! from thie negative.

Surveillance Photography

Surveillance photography is directed toward the

preparation of a photographic record of suspect

actions. The surveillance may center around an

I individual or around a location. In the case of an

, individual, there is interest in everything he does

and everywhere he goes. The surveillance

operator must be sufficiently close to the

suspect to record his location and his actions.

I This requires a maximum of ingenuity, the

careful selection of equipment, adequate

manpower, and much experience (and luck). In many cases, the task is impossible or impractiI cal, and even if pictures are obtained, they may

not be of direct use as evidence.

In the case of a location surveillance, there is interest not only in what happens at the location, but in the identity of all persons entering or leaving the premises. With luck, the surveillance camera can be set up in a concealed location,

such as an adjoining building, which is close

enough that a lens of moderate focal length

such as 135 or 200 mm can be used, and

oriented so that the light comes from behind the

photographer. In practice, ideal conditions are the exception and one must make the best of whatever conditions are found, and select equipment to suit the conditions.

The items most often looked for in surveillance

I photos are recognizable or identifiable faces.

The subject distance is generally large

compared to the subject size. Under these conditions, negative size is of much less imporItance than in other photographic work. What is of importance is image size, and this is determined by lens focal length and subject

j distance rather than negative size.

I Document Photography

i Document photography, from a photographic

f standpoint, is the simplest of all assignments.

All of the work is contained in two relatively well

L defined photographic areas: copying and

macro-photography. While all document work

will fall into one or the other of these two

categories, not all macro-photography in the law

enforcement field is document photography.

A major document assignment may be the

simple copying of personnel identification photographs so that prints are available to all the in- vestigators. Departments with a large volume of investigation will require a standardized copy

set-up which can reproduce, rapidly and effi- ciently, documents, photographs and other

paper originals with sizes of 28 x 36 cm

(11 X 14 in) and larger. The proper copying camera will provide reduced, same size or enlarged copies, from one-fifth or one-tenth

actual size up to five or more times actual size. Negative sizes for such cameras tend to be

much larger than normal, frequently 20 x 25 cm

(8x10 in) and larger. A large amount of document work will be at a one-to-one ratio.

For the smaller department, where a process camera cannot be justified, copy stands are

available for use with press or other type cameras, and greatly speed up the making of reduced size negatives from any flat original.
Normally, document work Is done on a slow,

fine-grained, high-contrast film. Panchromatic

film Is normally used, but a color-blind emulsion

may be required for some subjects. Filters are commonly used as required.

Documents may be photographed In their entirety, for presentation as evidence. Small

sections may be enlarged to show evidence of

alteration, erasures or forgery. Documents are commonly photographed for fingerprints, to determine whether a suspect handled them;

fuming and other techniques may be required to make the latent prints visible. Fluorescent photography may also be required, to show

tampering or alteration. Where enlarged

sections are necessary, the standard macro

techniques and equipment may be used or the

copy camera itself may be adequate. Under

these conditions, the medium format camera

6 X 6 cm (2 1/4 X 2 1/4 in) or 10 x 12.5 cm

(4x5 in) is little more trouble to use than a

small format camera. The photographs made

with the larger format camera will often be of better quality, particularly if a blow-up of a small

portion of a negative is required.

Motion Picture Photography

Motion picture photography has probably been

used In surveillance and arson Investigations more than in other law enforcement activities. Much detail can be seen In a motion picture,

such as a surveillance photograph of a suspect.

However, a still picture made from a single

frame may be useless for identification. In part, this Is because the subject Is moving and the in- dividual frames have too long an exposure to stop the subject's motion. It Isn't necessary to stop motion for a motion picture. In part, the

better apparent quality of the motion picture is due to the inherent ability of the eye to take a

detail out of one frame and add details from

each of the other frames projected so the

perceived motion picture apparently has much

more detail than any one of the Individual pic- tures from which It Is created. This adding-up

process, known as integration, contributes

much to the ability of the motion picture to convey information to the viewer.

Documentation or Record Photography

A less-traditional use of photography in law en- forcement is documentation (as opposed to document or documentary) or record photography.

Documentation Is the general use of simple,

non-professional cameras by rank and file officers to provide photographic information

where normally only notes and interviews would

be used. This is the area where automatic and

instant processing cameras (Polaroid and the new Kodak equipment) have their greatest

utility.

The purpose of a documentation picture is to add to the information which the investigator

records to pin down details that might be

remembered imperfectly and to preserve infor- mation which is difficult or very time consuming

to record properly by other means. These

photos are not intended as evidence or as substitutes for formal photography; they may be of

relatively low quality and have insufficient detail to allow enlargement. They are intended to supplement the normal photographs and investigator's notes. They are particularly valuable in situ- ations in which It is impossible, impractical, or too costly to assign a regular photographer to make a thorough photographic record. The

instant-process photograph is of particular value as an interim record that the first officer on the scene can get and use to convey information

until the lab prints can be made and distributed.

CAMERAS

El i

General Considerations

The convenience and efficiency with which any

type of photographic assignnnent can be accomplished is largely dictated by the camera that is used. With the exception of pictures taken by an

officer for informal documentation purposes, the

objective of nearly all photographic assignments

is to obtain professional quality prints suitable

for formal court presentation. This requires a camera that can be used under all types of

lighting conditions, and one which can produce

sharp images over a broad range of subject

distances. In many cases, it is also essential to have the capability of using different lenses.

The simplest of currently available cameras,

with slow lenses and fixed or zone focusing,

have little application to law enforcement photography.

The early cameras had lenses with very small

apertures, and used glass plates for negatives.

Focusing was done on a ground glass screen, and the plate was then inserted and exposed.

Since long exposures were required, only a

stationary subject could be photographed. All present-day cameras have evolved from these

simple direct-view cameras, incorporating a

variety of features to increase their utility and

take full advantage of improved film and lenses.

The development of roll film and better lenses

resulted in the design of a variety of view

finders, the simplest of which is simply a wire

frame which outlines the field of view. While

view finders enable one to aim the camera, even in the case of a moving subject, almost all suffer from a common problem—parallax. This

is a consequence of the fact that the view finder

must in general be located above or to the side

of the lens, and the camera lens and view finder see different aspects of the subject. The effect

of this displacement of the view-finder image

from that of the camera lens becomes signifi- cant at subject-to-camera distances of less than

approximately 3 m (10 ft), and at very long

distances when a telephoto lens is used. While a number of camera designs have incorporated

adjustments to minimize the problem of view

finder parallax, only the single-lens reflex has

completely eliminated it. Two types of shutters are used in modern cameras. Most medium and large format cameras

[6 X 6 cm (2 1/4 X 2 1/4 in) and larger film sizes], and cameras that do not allow lenses to be interchanged, use a between-the-lens

shutter. The exposure is controlled by leaves

which are located in the barrel of the lens

between the optical elements and which open

for the required period of time. The speed of a between-the-lens shutter is normally limited to a minimum duration of 1/500 second. The

majority of cameras that permit lenses to be in- terchanged use a focal-plane shutter. The exposure is controlled, at fast shutter speeds, by

moving a small slit-opening in a metal or fabric curtain across the surface of the film in a plane

located immediately in front of film. The focal- plane shutter permits fast shutter speeds, generally 1/1000 second or less.

It is generally possible to synchronize betweenthe-lens shutters to permit the use of a flash lamp or electronic flash unit at all shutter

speeds. The focal-plane shutter, however,

requires that a flash lamp or electronic flash be

used at the slow shutter speeds (generally 1 /60

second or longer), during which the entire pic- ture area is exposed simultaneously.

Since most negatives will be used to produce an enlarged print, film size must enter into the

selection of a camera. A 35 mm negative must

be enlarged eight times to produce the

20 X 25 cm (8x10 in) print that is normally

used for court presentation. The 6 x 6 cm

(2 1/4x2 1/4 in) negative need be enlarged

only five times to produce such a print. As the

negative size decreases, the skill of the photographer must increase, and the processing of the
film becomes more critical. It is apparent, then,

that the camera must be considered as one part

of the total photographic system. The trade-off factors relative to film size include 1) the ideal

size, from the standpoint of picture quality, for the particular task, 2) the lowest material cost,

obtained by the use of a small negative size and

only one size for all tasks and 3) efficiency in manpower use, which suggests the smallest

possible number of different types and a film size that requires the least time and lowest level of skill in both the taking and processing of pic- tures.

Based on the variety of assignments that is encountered, and the general considerations

concerning cameras that have been discussed,

it is evident that the selection of photographic

equipment is not a simple task. The general

characteristics of different camera types that are suitable for use in law enforcement photography are discussed in the paragraphs that

follow.

Coupled Rangefinder Cameras

Since the law enforcement photographer must

frequently take pictures at high lens speeds

(low f-numbers) and/or short distances, and

thus at shallow depths-of-field, accurate

focusing is essential. The coupled rangefinder camera was devised to accomplish rapid,

accurate focusing, particularly with moving subjects. In the superimposed image type, the

operator sees two separate images of the subject in a single eyepiece. The rangefinder is

adjusted until they coincide and become one. At

this point, the subject distance can be read off a

scale, if desired, but the camera lens has simultaneously been adjusted to the proper focus. In the split-image type of rangefinder, adjacent areas of the image are moved with respect to each other until a line which is continuous in the

subject becomes continuous across the image

dividing line in the eyepiece. The choice

between rangefinder types is primarily a matter

of personal preference.

Rangefinder cameras come in all film sizes from

35 mm to 10 x 12.5 cm (4 x 5 in). The largest

number of available models feature automatic

exposure control and non-interchangeable

lenses. Much smaller numbers have inter- changeable lenses. The top quality 35 mm

rangefinder cameras are designed as complete

systems, with literally hundreds of accessories.

Some professional photographers prefer these cameras and use no others.

Rangefinder cameras, with few exceptions, are simple to load and adjust. Focusing is positive,

giving a clear-cut in-or-out of focus indication

which requires less judgment than a ground

glass. Rangefinder cameras commonly use a

small optical viewfinder-rangefinder combination, requiring considerably more skill to visualize the finished picture than is required

with the larger matte screen image used in most

single lens reflex or press cameras. However,

this is largely a personal matter. Individuals

wearing glasses will probably have more diffi-
culty with this type of viewfinder than those who

do not.

The rangefinder camera is most suitable where

a small, quiet camera is required. In the 35 mm

size, where the choice is between the rangefinder and the single lens reflex types, the rangefinder's major advantage is its ability to determine

focus under poor light conditions more easily

than the single lens reflex. It also has a much

lower noise level than an equivalent single lens

reflex and, in general, is a lighter and significantly smaller camera. Thus it lends itself to situ- ations where the camera should be as inconspicuous as possible for a given film size. Parallax is a problem with the rangefinder camera and it is not the best choice for any task in- volving subjects at distances closer than 2.5 to 3.5 m (8 to 12 ft), or for use with long focus or telephoto lenses. With extremely wide angle

lenses, the parallax effect becomes very small

and may not be noticeable (such lenses generally require accessory view finders).

The initial cost of a rangefinder camera,

assuming comparable picture size, lens speed,

lens quality and optional features, will be significantly less than that of other cameras such as

the single lens reflex or twin lens reflex. There

is one major exception to this generality—the

top quality cameras are provided with a great

many features which are not found in the great

majority of rangefinder cameras; their prices are comparable to those of the better quality single

lens reflex cameras.

Press Cameras

The press camera, coupled with photoflash or e- lectronic flash supplementary lighting equipment, has been the starting camera and "workhorse" of the photographic units of many law en- forcement agencies. It uses sheet film rather

than roll film, although film pack adapters, roll- film holders (and Polaroid adapters) are readily

available. The size range is from 6 x 8 cm

(2 1/4 X 3 1/4 in) up to 10 x 12.5 cm

(4x5 in), the most common size. The increasing popularity of the smaller format cameras

prompted all manufacturers to discontinue

making the press camera several years ago.

Consequently, only used press cameras are

currently available; however, it now appears that

at least one manufacturer will start to make the

press camera in the near future.

The press camera is essentially a simple, direct view camera with a few added features, many

of which may be separately purchased options.

Press cameras provide for direct viewing of the

subject image on a ground glass, in addition to providing an optical viewer. For general police use, the coupled rangefinder is the most important option. It should be noted that many of the

older press cameras did not couple the rangefinder to the focusing system of the camera. Some press cameras also provide interchangeable cams to enable the rangefinder to automatically focus lenses of different focal lengths.

Slide and swing adjustments are the second

most important option. These adjustments, built into the front and/or back of the camera, allow

the position of the lens with respect to the film to be changed for distortion control. When the

ground glass screen is used, a tripod or other camera stand is mandatory. This enables the

press camera to be used for many of the

functions of a studio view camera. Recognize,

however, that the greater the number of adjustments that are provided, the more the accuracy

and reliability of the coupled rangefinder is jeopardized. For the law enforcement department with only occasional need for a studio

view camera, the press camera with full adjustment capability is an excellent choice.

Some press cameras are also provided with a

revolving or reversible back, which allows either

horizontal or vertical pictures to be taken

without turning the camera on its side. A

revolving back allows the film to be rotated

through any desired angle, while the reversible

back has two fixed positions: vertical and hori- zontal. Either is convenient, and both increase

the utility of swings, tilts, and other adjustments.

Almost all press cameras provide one viewfinder in addition to a ground glass. The separate

optical finder can be adjusted to match a full range of lens focal lengths, or a few specific

lenses. Some cameras combine the viewfinder

with the coupled rangefinder. This combined

viewfinder/rangefinder can be adjusted for
various focal length lenses. Remember, no viewfinder will enable the photographer to observe

the effects of view camera adjustments upon

the image.

Press cameras have been used for every type

of law enforcement photography and are an

ideal choice for many assignments, providing

maximum versatility with a miminum amount of special equipment. The level of skill required to realize the ultimate potential of the press camera is relatively high. The basic methods of operating the press cameras tend to encourage

the operator to utilize more care in setting up

than is usual with an automatic camera. The

result is fewer but more carefully planned pic- tures. The skilled photographer can use the

press camera on almost any assignment.

The press camera is much simpler mechanically

than many other cameras, resulting in higher reli- ability and easier repair. It is versatile, and the

large negative provides a safety factor in all operations from exposure to final printing.

However, it is large, weighs considerably more

than smaller cameras and is slow to operate.

Since it lacks a built-in exposure meter, the photographer must use a separate one. While its size and operating procedures make it unsuitable for some assignments, such as sur- veillance, the press camera is an excellent camera for all-around use.

The press camera is strictly a professional camera. Because of its limited market, the initial cost of the basic camera with one lens is high

compared to either the single lens reflex or the

rangefinder camera, as is the cost of accessories. This cost, however, will tend to be offset by

long operating life and overall reliability.

Similarly, the large negative size will result in a

relatively high cost per picture taken; however,

this will tend to be offset by the greater percentage of good and usable pictures that will be

produced.

Studio View Cameras

The studio view camera, normally referred to as

simply a "view camera," is the traditional camera by which the commercial photographer is known. All focusing and composition is accomplished using only the ground glass screen. For

inside studio work, it is essential, and it can be

used in the field as well. The view camera

provides a wide range of adjustments for changing the relative location and angular

position of the lens with respect to the film. The

distance between the lens and the film can be

adjusted over a wide range, from a small

fraction to three times the focal length of the

normal lens. View cameras are essentially

large-negative cameras; 20 x 25 cm (8 x 10 in)

is the standard size. Recently, a negative size of 10 X 12.5 cm (4x5 in) has gained popularity,

and view cameras using a negative size of 6 X 8 cm (2 1/4 X 3 1/4 in) are available.

Because of its large negative and ground glass

viewing screen, the view camera requires the

least skill to visualize the finished print;

however, of all cameras used for law enforcement photography, it requires the highest level of skill to set up and adjust.

The view camera is the only camera that has

been specifically designed to eliminate the

shape distortion that is present in most photographs. It also provides highly detailed ultra- closeup pictures; for example, a ten-times magnification of a thumbprint requires an image size

of 20 X 25 cm (8x10 in). It is likewise

adaptable for use in the photography of tool marks, morgue shots and forcible entry records.

The major features of all view cameras are quite

similar in principle, differing mainly in their precision of construction, the care with which

joints are fitted (this determines the overall
rigidity of the camera, particularly in larger

sizes), the ease with which adjustments can be

made, and the independence of adjustments

from each other.

View camera adjustments are basically swings

(rotation about a vertical axis), tilts (rotation

about a horizontal axis), and slides (horizontal or vertical displacement). Adjustments are more

easily and quickly made if the back (film holder)

swings and tilts are on pivot lines that intersect

at the center of the viewing screen surface. This

produces the minimum lateral, longitudinal, or focus shift of the film with respect to the lens

when the back is adjusted, and minimizes the

amount of compensating lens adjustment that

must be made. In some cameras, the back

pivots about its bottom edge instead of at the center of the film, causing a very large change

in focus as the back is tilted. Similarly, the lens

tilts and swings should be about axes that

intersect the lens axis at about the surface of the lensboard. This minimizes change in camera

direction to maintain the same view as the lens

is adjusted.

A good view camera will have "click stops" or some other means of positively setting all the

adjustments at the zero or centered position.

Sliding and rising-falling fronts and backs should

be designed so that their adjustments and locks are completely separate from the swings and

tilts, to prevent a change in one adjustment

from affecting others.

In a standard camera, the "plane of sharp

focus" is always parallel to the film, at right

angles to the optical axis of the camera, and at the distance from the lens for which the lens is focused. In the view camera, the plane of sharp

focus can be tilted at an angle with respect to the camera's axis and rotated around this axis as desired. As a general rule, the swings and

tilts of the film holder of the view camera are for the purpose of correcting distortion and those on the lens holder are for the purpose of keeping the desired part of the subject in sharp

focus. They may be used together or independently.

A modern view camera will have a tension

release on the spring back so that film holders

can be easily removed and replaced without

danger of moving the camera while trying to change a holder against a heavy tension spring.

Other available features include "fresnel" type

field lenses behind the viewing screens to brighten up the viewed image in the corners of the screen; sectional bellows to increase the

total lens extension for extreme enlargements

of fingerprints and small objects; revolving

backs allowing the film to be set at any angle

(all view cameras have a reversible back for horizontal or vertical pictures); reducing backs on

the larger cameras to take smaller size negatives; reflex viewers for convenience in using

the camera on a vertical copy stand for the

routine copying of documents and for macrophotography; and a wide variety of accessory film holders for both sheet and roll film and for instant-processing film.

Two basic types of view camera construction are found. The monorail has all parts mounted

on a single tubular metal rail, which may be

rectangular, triangular or of other non-circular cross section, to prevent rotation of the front or back standards around the bed. Traditional view

cameras, which were largely of wooden construction, used a flat bed with two parallel metal

tracks to guide the back and the front standard.

Both types of construction are still found. The

camera should be carefully checked to see if the total assembly rigidly locates the lens with

respect to the film when the camera is locked.

This is particularly important in the larger size cameras. All view cameras should have a

sliding base for attachment to the tripod, so that the complete camera can be balanced over the center of the support.

The view camera has several major disadvantages for some law enforcement assignments. It must be used on a tripod, since the camera

must be fixed during adjustment. Setting-up to take a picture requires more time than with

most other types of camera. It does not lend

itself to situations requiring rapid changes of lo- cation or viewpoint. It most often uses individual

film holders which must be loaded in a darkroom or light-proof changing bag. The total number of pictures that can be made without

returning to the darkroom for re-loading is
limited by the number of holders carried unless a changing bag is used. The camera is large in size and heavy compared to smaller film size cameras. Its ability to make short exposures is greatly limited by the long focal length lenses

used (which require stopping down for reasonable depth of field) and by the large

shutters they require (which generally limit the

shortest exposure to 1/50 of a second or

longer). Any operation in which a large volume

of diversified work is being done will require at least one view camera to be available for the

accurate portrayal of crime scenes, accidents

and some physical evidence.

As with the press camera, the initial cost of a modern precision view camera is higher than

the cost of precision 35 mm cameras. View camera lenses are always sold independently of the camera. View cameras have extended

service lives, with 30 years of use not uncommon. The cost of operation will be higher

per shot than for any other type of camera;

however, this is offset by the quality of the pic- tures that are produced.

Single Lens Reflex Cameras

The major characteristic of the single lens reflex camera (SLR) is a design that eliminates viewfinder parallax. An internal mirror reflects the

image from the camera lens to a viewing screen which enables the operator to focus and

compose the image exactly as it will appear on

the film. When the exposure button is pressed,

the mirror swings out of the way so that the

image is formed on the plane of the film. In older cameras, and in a few current models with

film sizes larger than 35 mm, once the mirror is tripped for exposure, viewing is "blacked-out"

until the camera mechanism is wound to advance the film for the next exposure. The

majority of SLR cameras incorporate an instant- return mirror which automatically returns to the

viewing position as soon as the shutter has

completed the exposure.

Virtually all SLR cameras incorporate lenses

whose apertures can be preset. The camera is focused at maximum aperture, and during exposure the lens aperture is automatically stopped

down to that preset for correct exposure. It is

possible, however, to set the aperture to the ex- posure setting to observe the depth of field. Most SLR cameras of current manufacture also

incorporate some type of built-in exposure

control, permit the use of interchangeable

lenses, and all provide either plug sockets or "hot-shoes," or both, for attaching either

photoflash or electronic flash units.

The film size of SLR cameras is basically limited to 35 mm, with more than 50 models available,

and 120 roll film, with approximately 10 models

to choose from. Most of the 120 roll film cameras produce a 6 x 6 cm (2 1/4 x 2 1/4 in) negative; however, a negative size of 6 x 8 cm

(2 1/4x3 1/4 in) is available, and two manufacturers recently introduced cameras that produce a negative size of 4.5 x 6 cm

(1 5/8 x 2 1/4 in).

Some older SLR cameras have exposure

meters that are integral to the camera but not coupled, requiring that the shutter speed and aperture be set manually after the correct exposure has been computed from the meter

reading. Most cameras of current manufacture use through-the-lens meter systems that are coupled to the shutter and aperture. SLR

systems measure the light from the scene in several different ways. Some systems measure

all of the light entering the lens, some average

all of the light with emphasis on the central area

of the image, others use a spot meter, and a few offer a choice of meter operation. While the

majority of exposure systems require that the

operator adjust either the aperture or shutter

speed to set the correct exposure, there are cameras which provide fully automatic exposure. All of these systems do a good job, but

the operator must recognize that the SLR may

indicate incorrect exposures under certain

lighting conditions, such as a small dark object

that is back-lighted, or a small brightly lighted

object silhouetted against a dark background.

The operator aware of the problem can easily correct for such lighting conditions. It should

also be noted that many SLR camera exposure

systems are very sensitive to light entering

through the viewing eyepiece. Photographers

who wear eye-glasses must be constantly alert to prevent inaccurate exposure readings.
Rubber eye cups with correcting lenses are

available to remedy this problem.

Many, but not all, of the SLR cameras offer inter- changeable viewing screens and eyepieces.

Often, the camera can be ordered with a nonstandard screen if desired. The available types

range from the plain ground glass (commonly

called matte), through various types of microprisms designed for specific focal length

ranges, to clear screens for aerial image

focusing. Some are available with a split prism

in the center of the field. The standard matte

ground glass is probably the best choice for all- round use and for the best visualization of the

final picture. The micro-prism is a pebbled

surface on which the image appears to break

up and disappear unless sharply focused. When

focused, the image is seen; when the image is not sharp, the pebbles or prisms are seen. This screen is good for use in poor lighting conditions. The split prism is also good for very

precise focusing and for focusing in poor light. The viewing screens normally have field lenses

to provide a bright picture from corner to corner;

this is standard in most SLR cameras.

The ability to use a variety of different lenses is a major advantage of the SLR camera. Both

bayonet and screw-in mounts are used to attach the lens to the camera, with most of the

higher quality cameras using the bayonet

mount. When selecting accessory lenses or

extension tubes, be sure to determine whether

the automatic aperture features of the lens

couple directly to the camera exposure control. Some of the 120 roll film size SLR cameras use

a between-the-lens shutter, and each accessory

lens must also have its own shutter. In general,

the range of accessories for the large format

SLR camera is more limited than that of the

35 mm camera. The SLR camera requires a minimum of operator skill to produce high quality pictures.

These cameras are necessarily complex in both

mechanical and electrical construction,

however, and are more prone to malfunction

than are the simpler cameras. Similarly, when

they do malfunction, repair can be expected to be more expensive than with a rangefinder or press camera. Also, mirror vibration is a problem that is peculiar to the SLR camera. If the camera is not firmly supported, the vibration

when the mirror moves from the viewing

position may be sufficient to blur the picture.

The extent of the problem varies depending

upon the design of the camera. High quality

SLR cameras have a control to manually lock

the mirror in the "up" position when the camera

is used with an unusually long focal length lens,

with a microscope, or for very long exposures.

In this position, the camera is "blind" and the

image cannot be seen. If the camera must be

used on a light tripod, use either a very short ex- posure (1/250 second or less) or a very long ex-
posure (1 second or more) to minimize the

effect of mirror vibration on the picture. Mirror

vibration may be more evident on a light tripod

with some cameras at shutter speeds between

1/250 and 1/15 second than if the camera is hand-held. The noise produced by the focal- plane shutter and mirror of a SLR is much

louder than that produced by a between-thelens shutter. The noise may be a serious disadvantage in covert surveillance photography.

Quality 35 mm SLR cameras can be purchased

for $300, with an automatic lens of normal focal length and built-in exposure control. The 120

SLR camera, however, is much more expensive.

In general, the prices of SLR cameras are exceeded only by the price of top quality view cameras.

Twin Lens Reflex Cameras

The twin lens reflex camera (TLR) had

widespread popularity, particularly in the period

before a large selection of SLR cameras became available. The TLR has two objective

lenses mounted one above the other. The top

lens, by means of a fixed front-surface mirror, reflects the image to a horizontal ground glass

viewing and focusing screen at the top of the camera. The image is right side up, but reversed

from left to right. The lower lens is the picture

taking lens and has a between-the-lens shutter

and iris diaphragm. The twin lenses are carefully

matched for focal length. They are mounted on

a common plate and are focused by moving

them together as a unit. The viewing lens has no adjustable aperture or shutter, and is normally supplied with a larger aperture to increase focusing accuracy and image

brightness. Unlike the SLR, the operator can

see the image at all times, even during exposures.

Most TLR cameras are manufactured in the 120

roll film size. The TLR camera is widely used in making personal identification photos. An electri- cally operated TLR, using 70 mm film in 100-

foot rolls, has proven very useful in departments

where a large volume of such work is done.

Using machine processing methods (Kodak

Versamat), consistently high quality negatives can be obtained in large numbers with a mini- mum of labor.

Several TLR cameras incorporate built-in exposure meters that are coupled to the shutter and

aperture, and adapters are available which

allow the use of 35 mm film or sheet film. Only

a limited number of attachments or interchangeable lenses is available. Eye-level finders are

also manufactured; these allow the direction of

sight to be parallel to the camera axis rather

than at right angles to it, and some' choice of viewing screen style is provided.

The level of skill required to operate a TLR is on

a par with that of the rangefinder camera. The

large viewfinder is an advantage to many

operators. The TLR camera does, however,

suffer from parallax. Since the TLR camera is not complex mechanically, it is a reliable camera and repair costs are relatively low.

The initial cost of a TLR camera with a single set of lenses will be about the same as for the

SLR of the same film size. While there are indi- viduals who prefer to use a TLR camera, it is not normally considered to be a top choice for law enforcement photography.

Motion Picture Cameras

The motion picture camera is essentially a motor driven still picture camera. The

mechanism automatically takes pictures and

advances the film at the rate of sixteen or more

pictures per second. Most cameras operate on

a cycle where one picture is taken for every

revolution of the motor drive shaft. During half of this revolution, the film is stationary and

exposed to light; during the other half revolution, the shutter is closed and the film is transported out of the picture aperture and

replaced with a fresh section.
Four sizes of film are commonly used for motion

picture work: 35, 16, 8, and Super-8 mm. Thirtyfive millimeter (the same size as used in 35 mm

still cameras), is used exclusively for commercial movies for theatre showing. Sixteen

millimeters has been the standard size for all documentary, educational, industrial, television,

commercial, and law enforcement movies for many years. Eight millimeter, once the standard

size for amateur use, is obsolete, replaced by

the Super-8, with a 31 percent greater picture area on the same film width (4.1 x 5.8 mm

frame size compared to 3.7 x 4.9 mm). The

choice for law enforcement purposes will be

either the 16 mm or the Super-8 size.

The big advantage of 16 mm motion pictures is

in the quality of the picture. The variety of equipment available for taking and projecting 16 mm

pictures, while not large compared with the

variety available in the Super-8 mm amateur

market, is adequate. They can be classified as

of high and very high quality. Sixteen millimeter

movie projection equipment is to be found all over the country in schools, institutions, clubs

and government agencies, and is also used by

private concerns for educational, training and in- formation purposes.

As far as picture quality is concerned, the situation is simple. Both 16 mm and Super-8 use the

same film width. The lenses of both sizes of cameras, if of standard quality, can image much

more information than the film is capable of recording. The 16 mm camera can provide pic- tures that cover almost three times as much

area with the same detail as the Super-8 or a

picture of the same area as the Super-8, but

with almost twice as much detail, enabling

objects to be detected in the 16 mm picture

that are half as large as the smallest detectable

object in the Super-8. A single frame of 16 mm

film can be enlarged to make a print up to 7.5 X 10 cm (3x4 in), as compared to 3.8 X 5 cm (1 1/2x2 in) for the Super-8,

before the detail begins to fall off so rapidly that

further enlargement is useless.

Sixteen millimeter equipment lacks some of the

convenience features that are taken for granted

in Super-8. Almost all Super-8 cameras are designed around a variable focal length or

"zoom" lens and automatic exposure control,

rather than interchangeable lenses. Sixteen milli- meter cameras are invariably built around inter- changeable lenses, requiring a minimum of three or four separate lenses. Variable focal length lenses are available as accessories for

all 16 mm cameras. They are very high quality

lenses with a normal focal length range of 10:1 and are correspondingly expensive.

In most cases, good motion pictures will require a higher order of skill on the part of the operator

than will good still pictures of the same subject.

In making motion pictures, it is common

practice to assign all of the processing to a motion picture processing lab having the

required special equipment and expertise to assure a high quality job. This simplifies the

operator's task. Movies are dynamic and

constantly changing. The operator must be able

to keep abreast of such changes and anticipate

them, or the quality of the movies will be greatly

degraded. The operator must be alert and per- ceptive over much longer time periods and to many more things than is normally required in taking still pictures.
Two major uses for movies in law enforcement

photography are surveillance photography and

in recording tests and behavior in "driving while

under the influence of alcohol" (DWUTIA)

arrests. Where surveillance is from a fixed location and the larger size of the 16 mm equipment

is not a critical item, jeopardizing the large ex- penditure in labor and time by the use of the

lower quality Super-8 would not seem justifiable.

For recording a large number of DWUTIA tests, the lower operating cost plus the conditions

under which the movies are made would make

Super-8 the logical choice.

All 16 mm equipment will be relatively high in

initial cost, although in general the quality will be

high. There is a good supply of used 16 mm

equipment, and high quality rental equipment is available for the infrequent user. The relative operating cost will be about 6 times as high for 16 mm as for Super-8, based upon film price

and processing cost for a single original in color, using the same type of emulsion, and for the same running time in both sizes. Local conditions with respect to processing facilities and

film discounts will cause this figure to vary from

department to department.

Instant Process Cameras

There are several instant process systems of photography. Prior to 1976, there was only one, manufactured by the Polaroid Corporation.

Eastman Kodak introduced an instant process

film and camera system in the spring of 1976. In one process, a paper negative is exposed in a

special camera or adapter. It is then automatically coated with a viscous developing agent and

rolled into contact with the paper positive as the

"sandwich" is removed from the camera.

Printing proceeds to completion by a chemical

diffusion process (rather than exposure to light)

between the sandwiched emulsions until they

are separated in normal light. This requires ap- proximately 10 seconds for black and white film (hence the instant process designation). It is a

little longer for color film. After separation, the

black and white positive requires a surface

cleansing and coating with a preservative,

applied with a swab. In the color Polaroid

process, this step has been eliminated. Both

Polaroid and Eastman Kodak manufacture color

films that do not use a separate paper negative.

Pictures taken with those films require several

minutes to fully develop the image.

At the present time, the Polaroid Corporation

manufactures a full line of cameras and one

"Sixty-Second" camera is available from an

independent manufacturer. The complexity of these cameras varies from a simple scale

focusing unit to a completely automatic, motor

drive, folding, single lens reflex (the only folding

SLR available). All of these cameras, including

the simplest, utilize electronically controlled

shutter speeds to automatically control the exposure within the range of conditions that a particular camera has been designed to cover. The

Polaroid Corporation has also introduced cameras with automatic focusing. These cameras

are simple to operate, requiring minimal

operator skill. The picture sizes of the Polaroid cameras are limited to 6.5 x 8 cm

(2 1/2x3 1/4 in), 8x11 cm

(3 1/4 X 4 1/4 in) and 8 x 8 cm

(3 1/8x3 1/8 in) in the case of the SLR.

Eastman Kodak introduced two models of its camera during 1976, and plans to expand the

line to include more sophisticated cameras. The

Kodak cameras also incorporate automatic ex- posure control. Their picture size is 6.5 x 9 cm

(2 1/2x3 1/2 in).
Adapters are available which allow instant

process filnn to be used with view cameras,

press cameras, and 35 mm SLR cameras.

Polaroid film is available for use in the

10 X 12.5 cm (4 X 5 in) size, and a black and

white film is manufactured which produces both a positive print and a negative. The negative

must be fixed in a special hypo solution immediately after exposure. The resolution of this film, unlike that of most instant process film, is comparable to that of conventional photographic film.

The big advantage of the instant process camera is the ability to see the picture immediately.

This is important to the beginner or infrequent

user, for it allows errors in framing, focus or ex- posure to be corrected at the time the pictures are being taken. With the conventional photographic process, such errors are rarely detected

in time to allow corrective action. Instant process cameras are therefore excellent for use

in photographic training. From a law enforcement standpoint, however, the ability to use the

picture as soon as it is taken may be more important than the ability to correct mistakes.

There are two methods of obtaining multiple

prints from the instant camera process (unless

the picture is taken with a positive-negative

film): taking as many pictures as required at the

time of photography, or copying the original

print using conventional photographic

processes to make a negative. Taking duplicate

pictures is impractical for any subject involving

motion, living subjects, facial expressions, or

position of moving vehicles. In outdoor scenes, even the lighting changes. Multiple picture

taking can only be used under special circumstances. The use of conventional photographic

processes to copy an instant process print

produces good duplicates, but it also neutralizes

almost every advantage of instant process photography. The end result is that more labor must

be put into every print than if it had been made

by conventional methods initially. In addition,

the instant process pictures lack the detail of conventional prints, picture quality is necessarily

degraded by the process of copying, and an en- largement cannot be made without significant

loss of detail. It may not be possible to make an

enlargement to show minute detail that may be

desired long after the original picture has been

made.

The instant process camera system is not an in- expensive system to use, particularly if a

substantial number of pictures are to be made.

Initial equipment cost will be less than for the

35 mm automatic camera. For situations where

widely varying numbers of pictures are needed

at infrequent and irregular intervals, it is ideal. However, there is no way to use production-line

methods to reduce the cost per picture as the

total number of pictures increases. A roll or pack of film, which costs many times the cost of equivalent materials for the same number and

size of conventional photographs, costs the user the same whether or not it produces pic- tures. However, the costs are relatively fixed

and predetermined.

There are a variety of special purpose cameras

and accessories available, and the instant

process camera can be an outstanding tool for the law enforcement official. Like other tools, it should be used where its characteristics fit the

job: informal documentation, supplementary aid on smaller cases that do not require formal photographic evidential coverage, mug shots,

internal security badges and similar uses.

Instant process photography is a supplement to, and not a substitute for, conventional photography in the law enforcement field.

Automatic Cameras

An automatic camera is one in which the normal

picture-taking actions of threading the camera

and choosing the aperture and shutter speed

have been so simplified that the user need have

no knowledge of their principles in order to perform the operations properly and obtain a

usable picture. The automatic camera senses

the exposure the subject requires and, if it cannot adjust to these requirements, either

signals the photographer that a mistake is about

to be made or prevents the exposure.

The automatic camera has two features that most single lens reflex cameras do not have.

First, it uses an already threaded roll of film in a

plastic cartridge that can only be placed in the
camera in one position, the right one. The car- tridge is notched to set the camera properly for the speed of the film in the cartridge, rather

than requiring the operator to set the film speed. Secondly, the exposure control system senses the light coming from the subject and automatically adjusts the camera to meet those

conditions, rather than indicating the condition

in some manner and requiring the operator to do the adjusting. If the light is insufficient for the

needs of the camera and film, a warning signal

tells the operator to use a flashbulb. Putting in the flashlamp automatically programs the camera to properly expose for the flashlamp and

subject, either from the distance for which the camera is focused in the simpler automatics, or by closing the shutter when the proper amount

of light has been reflected from the subject in the more sophisticated ones. At least one manufacturer has announced the availability of an

auto-focusing 35 mm camera.

These cameras (the highly popular Kodak

Instamatic is a typical example) have met a

definite need in the law enforcement field. It should not be forgotten, however, that an auto- matic camera cannot select for an investigator

those elements which are important to be

recorded in a picture. Directions for camera operation are in the instruction manual that comes

with every camera. Directions for making good

pictures are much more difficult to communicate. Photographers devote a good

part of their professional careers to perfecting

this technique. The automatic camera's

usefulness will be determined by the operator's

judgment in selecting what he photographs, as much as by the camera's technical features.

In addition to the cartridge-loading automatics,

there are a number of automatic cameras that use standard 35 mm film magazines. Loading,

in these cameras, has been simplified to placing

the film in the camera, inserting the end of the

film in a slot and closing the camera. In addition, the film speed must be set into the camera by the operator. This type of camera is often provided with greater capabilities than the

average automatic camera, in the form of faster and higher quality lenses, higher maximum

shutter speeds and, in some cases, interchangeable lenses or front lens elements, giving some

choice of focal length. They find considerable use in covert surveillance where a small inconspicuous camera is required but something

larger than the sub-miniature negative is necessary.

Sub-Miniature Cameras

A sub-miniature camera is any still camera that uses film which is smaller than 35 mm in width.

The classic example of the sub-miniature camera (the Minox, which has been around since

pre-World War II) uses 9.5 mm film to produce

50 pictures approximately 8x11 mm. Most of the current sub-miniatures, however, are based

on a film width of 16 mm and produce pictures

from 10 X 14 mm to 13 x 17 mm. Anyone who

has tried to get good identification pictures from
16 mm motion picture records will appreciate

some of the difficulties to be expected in the use of the sub-miniature camera.

If a camera has a lens of good quality, the film

is always the limiting factor in the camera's

performance. The theoretical maximum

resolution that can be obtained from any f/2

lens is approximately 700 line pairs per millimeter; many available lenses are almost that good.

There are very few films that approach that

figure, however. Mostly these are extremely

slow, very high contrast films that are completely unsuited to the purposes for which

we would like to use them. If effective use of sub-miniature cameras is required, it is suggested that comparative tests be made of as many different types of film as possible.

From this, identify film with the desired characteristics. Since packaging of film for sub-miniatures is not standardized, it is common practice

to obtain a store of cartridges to fit the camera

and load one's own film. Obviously, processing

is critical to the quality of pictures taken with

sub-miniature cameras.

Cameras using the instant loading 110 size film cartridge which produces a 13 x 17 mm picture

should also be considered sub-miniature. These

cameras, made by all of the major manufacturers, follow the general automatic operation of the Instamatic system except for camera size

and picture format. The Pocket Instamatic is not

just a camera but a coordinated system of cartridge color film, camera and projector,

designed for producing transparencies of color

negatives and prints. It may be of particular use

in some covert surveillance, since it is an amateur type of camera, rather than a professional type, and may attract less attention for

this reason.

Fingerprint Cameras

The need to conveniently record fingerprints, at a period when cameras specifically designed for close-up, small object photography were not

available, led to the development of the tradi- tional "shoe-box" fingerprint camera. This was

a complete unit of camera, lens, film, lights and

batteries, built in the form of an open-ended

box. The open end of the box was placed

against the surface on which the print was

located, the lights were turned on, the shutter was released, and a same-size negative of the

print resulted. In spite of all the progress that has been made in other areas of photography,

the same fingerprint camera is being used

today.

A fingerprint camera is a simple camera,

designed to do one job: make full-size records

of fingerprints, single or whole hand (or similar marks, such as ear-prints). It is a specialpurpose camera which requires basically no

operating adjustments by the operator, and has

its greatest use as a tool for non-photographic

personnel. If its reliability is good and its operation foolproof, it could be a useful piece of equipment. Too often, the available types of fingerprint cameras, while simple to operate, are not automatic in the sense that they warn when

things are going wrong. A weak set of batteries

would probably not be detected until the

operator received his underexposed negatives.

Instant fingerprint records can now be obtained

by an instant process camera kit which utilizes a

framing guide fastened to the front of the camera. When this is placed against a flat surface, it steadies the camera, keeps it the proper

distance from the surface to assure a sharply

focused picture, and outlines the area of the

subject that will be covered. Lighting must be

separately supplied. Also, close-up attachments

are obtainable for use on the 10 x 12.5 cm

(4x5 in) press camera specifically for taking
fingerprints. Fingerprints would seem to be an assignment made to order for the single lens

reflex camera with macro lens and one of the

automatic electronic flash units. Either a tripod or one of the many macro or close-up attachments similar to that provided on the instant

process kit would enable most fingerprint assignments to be handled with comparative ease.

Although at first glance the fingerprint problem

would seem to be one that could well be

handled by an automatic type of camera

modified for the purpose, the wide diversity of surfaces on which prints are found and the dif- ferent techniques required to make them visible make the problem more complex than a cursory

examination would indicate. For this reason, the

experienced photographer with his more

versatile equipment will probably still be

required to assure good photographs.

Camera Selection

The great popularity of the 35 mm single lens

reflex camera for amateur use has made avail- able a large selection of equipment of high

quality and reasonable price. Most of it has

been designed to appeal to the inherent

tendency of photographers to equate

excellence of equipment with excellence of pic- tures. Excellence of equipment in this context

normally is taken to mean the degree of automatic operation built into the camera rather than

the degree of reliability, adaptability, resistance

to normal field abuse, and a long normal life without maintenance. The law enforcement

official choosing photographic equipment

should keep this and the following points in mind.

A. When one particular type of subject only

must be recorded, and it can be closely

controlled, automatic equipment can do a much

better job with less operator skill than manual

equipment.

B. Automatic equipment is also useful for the

production of relatively good and consistently

exposed negatives by completely untrained

operators under a variety of unfamiliar conditions.

C. Where overall picture quality is the main

criterion, there is no substitute for large negative size. No matter how good a small negative can be, a large one of the same quality will always produce a better print. Large negatives

require less magnification, and any imperfections will be less noticeable.

The size of the subject that is to be photographed is one of the first concerns when selecting a camera, for it is a limiting factor in the

size of the image that will be recorded. Table 1 presents a general classification of subject size.

Table 1. CLASSIFICATION OF SUBJECT SIZES

Size

Classification Subject

Dimensions

Exannples of Typical Subjects

Large Area Over 1 7m

(50 feet)

General area, large building, general fire scene, mob scene, general street view, inside of large hall or arena, scene of accident or crime. Medium Area 3 to 17m

(10 to 50 feet) Large room view/, wrecked car, skid marks on road,

interior vandalism, crime location, location of bodies,

interior accident. Smali Area 60cm to 3m

(2 to 10 feet) Portion of room, general view of very small room,

position of body, print of entry, tire or footprint, large weaporis, large articles of evidence, documents. Very Small Area

1 5 to 60cm

(1/2 to 2 feet) Documents, handprints, wounds, small articles of evidence,

tools, weapons, cigarette and cigar butts, damage at point

of entry. Macro

^ Less than 1 5cm

(1/2 foot) Fingerprints, jimmy or tool marks, paint chips, bullet

holes, cartridge cases and bullets, hair and skin fragments,

signatures.

* Macro is a prefix indicating that the image must be larger, compared to the subject, than is usual in photography.

This is done by using special photographic lenses as opposed to the use of a microscope.
Obviously, large format cameras offer a distinct advantage when photographing large or medium size subjects, if small detail is critical to the usefulness of the photograph. Image size is discussed in more detail in the section of this guide that follows.

The selection of a camera will also be

influenced by the manner in which the subject is illuminated (either by existing light or supplemental lighting), or if the subject is moving or

stationary.

While this guide places emphasis on the selection of equipment to obtain the highest quality

photograph possible, not all choices can or should be based solely upon negative quality.

Rather, the person making the camera selection

must use careful judgment based upon a

multitude of factors such as size, weight, level of operator skill, adaptability to many assignments, or the ability to handle fast action. A

checklist of camera characteristics that should

be considered when selecting a camera is at the end of this section. One special characteristic is conspicuous by its absence: personal pref- erence or known skills of your photographers

with specific types of equipment. In using the

checklist, you can set your own requirement for each characteristic based upon what you would

consider to be ideal for your application and

rate the various cameras that you are considering accordingly.

CAMERA

SELECTION

CHECKLIST

1. Overall size

2. Total weight

3. Time to set up

4. Operating skill 5. Available accessories

6. Initial cost (camera & one lens)

7. Relative cost/picture

8. Maximum lens aperture

9. Maximum magnification

10. Maximum negative area

11. Versatility 12. Distortion control

13. Types of film used

14. Maximum shutter speed

15. Instant process available

16. Follow fast action

17. Ultra wide angle lens

18. Automatic exposure control

19. Conspicuousness

20. Interchange lenses

21. Number of lenses available
25
LENSES

Depending upon the assignnnent, the photographer will need a wide-angle, normal, or longfocus lens to record the subject of interest. Aside from the obvious requirement that the

lens must fit the camera that It will be used with,

the selection will boil down to focal length

(which determines the size of the image) and

f-number (which determines how bright the

image is). Naturally, one is also interested in the

limits of use of a specific lens, such as general

purpose, macro, or process.

In most cases, one will select a lens that is provided by the camera manufacturer and

designed for use on that particular camera. The

lens mounts will fit properly and assure that the

lens is in the proper position for focusing. It also

assures that the automatic or preset diaphragm

used on so many single lens reflex cameras will be properly mated mechanically to the

mechanism that is a part of the lens. The manufacturers of most cameras with interchangeable

lenses provide some selection of lenses of varying characteristics for use on their cameras. Some 35 mm single lens reflex cameras

provide a choice of 20 or more lenses of various focal lengths, speeds, angles of view

and special use characteristics.

Why look elsewhere than to the original manufacturer of the camera for an additional lens?

Two reasons. Not all camera manufacturers are

lens manufacturers, although a great many are. You may be forced to buy a Brand-X lens if an
accessory lens is wanted. In the professional

field, particularly with press and view cameras, it

is common practice for the photographer to make his own selection of lenses and have

them fitted to the camera of his choice. Some

lenses that eminently fill special needs are avail- able from one or two manufacturers only, and

such manufacturers are normally lens

specialists and not camera manufacturers.

The great variety of 35 mm single lens reflex cameras has brought into the market a large selection of "universal" Brand-X lenses, designed

to fit many makes and models of single lens

reflex, rangefinder and other 35 mm cameras.

All of these lenses are made by independent

lens manufacturers and they supply adapters to

fit the lenses to most popular cameras. Why

use Brand-X lenses for professional work? In general, they are of high quality, as good as those furnished by the camera manufacturer.

Many times, they provide an in-between selection of focal length, speed or some other characteristic desired by the professional, that is not

available in the camera manufacturer's line of lenses. Because of larger production in some

popular models, prices may be lower than for the equivalent lenses as available from the camera manufacturer. The user of good quality

"universal" accessory lenses will normally be

satisfied with them, but he must assure himself

that the desired lens is properly adapted to the

particular camera on which it is to be used.

Image Size

The size of the image that a lens forms is determined by three things: the size of the subject, the distance from the camera to the subject, and the focal length of the camera lens. The ratio between the size of the image and the

focal length of the lens, for subjects which are

at least 10 focal lengths from the camera, will be the same as the ratio between the size of the subject and its distance from the lens.

Focal length is an inherent "designed-in"

property of every lens. For a simple thin lens

made of a single piece of glass, it is the

distance from the center of the lens to the film when a very distant object is sharply focused on

the film. Photographic lenses are thick lenses

(combinations of a number of simple lenses),

however, and methods of measuring the lens to

film distance are complicated. There is no

readily identifiable point, in a lens which may be

two or more inches thick, from which to measure; so we speak of the "equivalent focal length" of a photographic lens, referring to the

focal length of the simple lens that would give

the same image size. All photographic lenses

are marked with a focal length. This is a nominal value and is normally within 5 percent

of the actual focal length.

For the rapid calculation of image size, it is convenient for the photographer working in the field to know the "coverage" ratio of each lens-camera combination which he uses. This figure will quickly give him, with only a rough mental

calculation, the total field of the camera. The

maximum dimension (height or width) of the negative divided by the focal length of the lens is the coverage ratio. For any object at any

distance, the distance times the coverage ratio for that lens-camera combination will give the

maximum field of the camera.

For example, a 35 mm camera (36 mm maximum negative dimension) and a 50 mm lens

have a coverage ratio of 36/50, which equals

0.72 or approximately 7/10. If the subject of interest is 100 feet from the camera, the total

field of view is 7/10 of 100, or 70 feet. A 6-foot

man is a very small portion (somewhat less than

10%) of the field of view, so his image is going

to be an equally small percent of the total length of the picture (less than 35 mm). Notice

that it does not matter in what units the lens

focal length is marked, as long as you figure the

coverage ratio using the same units for the

length of the negative. Similarly, the calculated

figure for the camera field of view will be in the

same units you use to measure the distance:

meters, feet, yards, etc.

As another example, consider two cameras, a 16 mm movie camera and a 35 mm single lens

reflex, both with 50 mm lenses. For the 16 mm

camera, the coverage ratio is 10.3/50 or approximately 2/10. For the 35 mm camera, the

coverage ratio is 36/50 or approximately 7/10. At 20 feet, the field of view of the 16 mm camera is 2/10 times 20 or 4 feet. The picture will
include only 2/3 of a 6-foot subject. For the

35 mm camera at 20 feet, the field of view is 7/10 times 20 or 14 feet. The 6-foot subject will cover about half the negative. Table 2 gives the

coverage ratios for some commonly used image

sizes and lenses.

Lens Speed

Lens speed is a subject of interest and

confusion to beginning photographers and to those not well versed in optics. A camera is like a closed room with a window in the center of one end wall, and the film on the center of the

opposite wall. The light reaching the film through a large window will be quite bright,

while much less light will reach the film through a small window. Similarly, for a given window

size, the amount of light on the film will decrease if the room becomes longer. The

amount of light reaching the film, then, is a

function of the length of the room (the focal

length of the lens) and the size of the window

(the diameter of the aperture or diaphragm of the lens). Specifically, the amount of light

reaching the film is determined by the ratio of the focal length to the diameter of the aperture.

Table 2. FIELD COVERAGE RATIOS

Lens Focal Length

(mnn) 24 X 36mm 7.5x1 0.3mm

Picture Size 6 X 6cm 6 X 7cm 10 X 12.5cm

15 2.4 .69 25 1.4 .41 2.4 2.8 35 1.0 .29 1.7 2.0 3.6 50 .72 .21 1.2 1.4 2.5 58 .62 .18 1.0 1.2 2.2 75 .48 .14 .80 .93 1.7 80 .45 .13 .75 .88 1.6 90 .40 .11 .67 .78 1.4 100 .36 .10 .60 .70 1.25 135 .27 .076 .44 .52 .93 150 .24 .069 .40 .47 .83 165 .22 .062 .36 .42 .76 180 .20 .057 .33 .39 .69 270 .13 .038 .22 .26 .46 375 .096 .027 .16 .19 .33

This ratio is called the relative aperture of the

lens. The amount of light reaching the film will be the same for any specific relative aperture,

regardless of the focal length of the lens. The

relative aperture is the f-number or stop of the

lens; if the focal length is twice the diameter of the aperture, the ratio is 2/1, or 2 and it is written as f/2. Similarly, if the focal length is four times the diameter of the aperture, the ratio

is 4 and the f-number is f/4. Note that the size

of the aperture for a given focal length

decreases as the f-number increases. Thus, the

brightness of the image on the film decreases

with increasing f-number.

It is convenient in photography to vary the

length of time that light is allowed to act on film by factors of two to one. So lens diaphragms

are marked with a series of relative aperture

numbers that have a two to one exposure factor

between adjacent stop numbers. The opening in the lens diaphragm is circular, and it is the area

of the aperture that determines how bright the

film image is. Doubling the diameter of a circle makes its area four times as great; thus, our f-numbers will have an inverse-square rela- tionship with the required exposure. If we
multiply the f-number by two, the diaphragm

area will be decreased by two squared or four

(requiring an exposure duration four times as

long as the original to produce the same effect on the film). Since it takes two multiples of two

for the new exposure, it is spoken of as an exposure increase of two stops.

Table 3 will make this a little clearer. It compares, starting with a relative aperture of

f/1.4, the standard f-numbers which are normally used for marking relative apertures,

the total number of stops of exposure change

which they represent, and the relative brightness of the image on the film with respect

to the image at f/1.4. In going from f/1.4 to f/22

(a normal range for a lens of this speed) the ex- posure is increased by eight stops and the

image on the film is 1/256 or 0.0039 times as

bright as the original image.

Most lenses have the maximum relative aperture (smallest f-number) marked on the lens and

as the first stop on the aperture control. The

next stop marked on the aperture control will be

the next larger one of the above series of standard stops. For instance, on an f/1.7 lens, the next marked stop would be f/2. This does not

represent a change of a full stop but only

seven-tenths of a stop from maximum aperture.

This must not be forgotten since the change for the first aperture stop is not always a full stop on a great many lenses.

Speed in a lens, as determined by the relative aperture, lets us know how long we have to expose the film. Using table 2, we find that with an f/1.4 lens, the light can be one-eighth as

bright as with an f/4 and still allow the same

length exposure. For the same brightness of

light on the subject, the shutter speed can be

shortened by a factor of eight. For the law en- forcement photographer, lens speed is of the

greatest value in a covert surveillance situation

where supplementary illumination cannot be

used and the difference between an f/1.2 and

an f/1.4 lens may mean not getting a picture

with the f/1.4.

Depth of field is another important factor. The

nearest object of interest and the most distant one must both be sharply focused at the same

time. Whether or not they will be is dependent

on several factors, all of which must be

balanced against each other. A large depth of

field is particularly important when the amount

Tables. LIST OF STANDARD f-NUMBERS

Stops -1 2345678

f-Number 1.4 2.0 2.8 4.0 5.6 8.0 11 16 22

Relative Brightness 1

1.0 1/2 1/4 1/8 1/16 1/32 1/64 1/128 1/256
of enlargement to be given the negative is great. A large depth of field is obtained when

the f-number of the lens is large, the focal length is short, and the nearest object distance

is large. Conversely, a very shallow usable

depth of field is obtained when the lens

f-number is small, the lens focal length is large,

and the near object is very close to the camera. These requirements are obviously conflicting,

and the lens aperture or f-number is normally

the one which can be most easily adjusted to get the desired depth of field. Focal length must

be chosen based on required image size; the near and far objects are where we find them;

and the negative size determines the amount of enlargement. The working photographer quickly

finds that his sharpest pictures tend to be shot

at large f-numbers.

I

Still other factors are pertinent to the subject of lens speed; speed is obtainable only by the

sacrifice of other qualities. The sacrifices

required for extreme speed in lenses used

primarily for general law enforcement photography do not produce corresponding benefits.

Covering power must be sacrificed for speed; in general, even moderately wide angle lenses will be one or two stops slower than lenses with

smaller angular coverages. As speed is increased, size and weight go up rapidly. A twostop increase in speed automatically doubles

the diameter of the lens. In addition, the internal construction must be made more complex,

requiring 8, 10 or even more optical elements

where 4, 5, or 6 were sufficient on the slower

lens. The more complex lens will be physically

longer than the simpler one, and this in turn requires still larger diameter front and rear elements to prevent light cut-off or vignetting.

The weight and size are thus increased still more.

Focusing range, in general, is also sacrificed for speed. The more complex lens designs are much more sensitive to changes in object

distance than the simpler designs. An f/1.2 lens

may show a definite fall-off in sharpness when

used at 3 feet while a corresponding f/2.8 lens

may give sharp pictures down to 12 inches.

Such problems are generally only discovered by

actual experience with the lens, at which point it

is too late to correct the problem. Many ultra- fast lenses cannot be stopped down beyond

about f/11 or f/16, and neutral density filters must be added for bright light conditions. For

general purpose work, lenses with apertures in the range of f/2 to f/4 will be found adequate,

with those faster than f/2 reserved for special

Depth of Field
situations where the maximum obtainable lens

speed is the only way to get a picture.

Lens coatings, too, must be considered.

Whenever light strikes the surface of a glass

lens, about 4 to 5 percent of it is reflected back

from the surface, a much smaller amount is absorbed in passing through the glass and the

balance is transmitted through the glass to the

opposite surface, where again about 4 percent

is reflected back to the first surface. Thus,

about 8 percent of the light is lost for every

element in the lens which is bounded by air on

both sides. For a 6-element uncoated lens, the

total light leaving the lens is about half of that entering it. With a complex zoom lens with 1 5 to 20 elements, the light leaving the lens would be

only a small part of that entering.

By coating each lens surface with a layer of magnesium fluoride or similar material, the

reflection losses can be reduced. The layer

must have a uniform thickness of exactly 1 1 A of a wavelength of light. With this technique, the

light reflected at each surface for one particular

wavelength can be reduced to about 1/2

percent, with an overall reflection for all wavelengths of 1 to 2 percent per surface

instead of the normal 4 percent or more. By

using more complex coatings with 7 or 8 layers

and different materials, the reflectance per

surface can be brought down to an overall

figure of 1/2 percent. These multi-layer highefficiency coatings are being increasingly

applied to newly designed lenses. The resulting

increased light transmission is of great value in complex zoom and extreme wide angle lenses

of many elements. What is of equal importance

is that the light from internal reflections in an uncoated lens may be reflected back to the film

in the form of stray light that fogs the film and

decreases the image contrast, degrading image

resolution. The multi-layer coating prevents this degradation, which is particularly noticeable in a

back-lighted subject.

Angular Coverage

As previously discussed, the size of the image

formed by a lens depends solely upon the

distance to the subject and the focal length of the lens. The field of view of the lens can be

visualized as a cone which extends forward

from the center of the lens, spreading out around its optical axis to infinity. The angle

between the sides of this cone is the angular

coverage of the lens. Similarly, a second cone

extends from the lens on the image side of the

lens to the film; the angle of this cone is the same as the viewing angle. Whether the image

completely covers the negative depends upon

the focal length, the angular coverage, and the

size of the negative. The image that is formed is circular, while the negative is square or rectangular. The dimension of concern, then, is the diagonal measurement of the negative.

It is readily apparent that if the area of the

image circle just covers a 35 mm negative, it

will only partially cover the area of a 6 x 6 cm

negative. Thus, if the same focal length lens is to be used on a larger film size camera, the

angular coverage of the lens must be increased

to provide an image at least as large as the film. In the case of a view camera, which has distor- tion control adjustments, the angular coverage

must result in an image area even larger than

the film size. The lens manufacturer will state angular coverage either in degrees or in terms

of the maximum film size that will be covered by

the lens when it is focused at infinity.

The normal lenses for any camera will have an

angular coverage of 45 to 50 degrees when

used on the film size for which they were

designed. Their coverage ratio will be approximately 0.7 to 1.0. They produce a pleasing per- spective in the negative and will lead to natural appearances and convenient viewing distances.

In movie cameras, the tendency is to use a normal lens with a considerably smaller angular

coverage, generally about 30 to 35 degrees.

This is partly for convenience in filming; the subject is further from the camera and so does not go out of focus so easily, as it moves around.

Table 4 lists the length of the film diagonal, the

normal lens focal length (which is approximately

equal to the diagonal) and the minimum angular

coverage for several picture sizes.

The law enforcement photographer will have

frequent need for other than normal focal length

lenses. These too are tabulated in table 4. Wide

angle lenses are defined as lenses that are
designed to provide a much greater than normal

angular coverage when used with the picture

size for which they were designed. They are always of shorter focal length than the normal

lenses for a given picture size. This has lead to the misconception that all short focal length

lenses are wide angle, which is incorrect. All lenses with angular coverages exceeding 50 to 60 degrees are wide angle lenses. Their

coverage ratios will be much greater than 1. Even a wide angle lens can become a normal

lens if it is used on a sufficiently smaller film size than it was intended for, because of the

reduced angular field of the image that is recorded. Lenses with coverage angles of 100

or more degrees are generally considered to be

extreme wide angle lenses, although there are no hard and fast limits. Fish-eye wide angle

lenses covering 180 degrees to 220 degrees

are available for many picture sizes and camera

models. These extreme coverages are obtained

only at the expense of great distortion. Straight

lines a short distance from the lens axis are

greatly bowed and appear in the picture as though curved. Such lenses have little application to law enforcement use.

The opposite of the wide angle lens is the narrow angle or long-focus lens, commonly miscalled the "telephoto" lens. The term telephoto,

although commonly used, may be incorrect;

optically, a telephoto lens has a special design.

It is composed of two combinations of elements, a negative or diverging combination

nearer the film, with a positive or converging

combination ahead of it. Its distinguishing charTable 4. ANGULAR COVERAGE FOR DIFFERENT PICTURE SIZES

Angular Coverage

Film Size

Picture Area

1 J -j^i, diagonal

length and width , ^

,

normal

focal length angle

(mm) (degrees)

wide angle

focal length angle

(mm) (degrees)

narrow angle

focal length angle

(mm) (degrees)

Super-8 4.1 X 5.8mm 7.1 13 31 09 43 23 18

9.5mm 8x11 mm 14 15 50 NA NA NA NA

110 Cartridge 13 X 17mm 21 23 50 NA NA NA NA

16mm 7.5 X 10.3mm 12.7 25 29 15 46 100 7 35mm 24x 36 43 50 47 28 75 180 14 126 Cartridge 28 x 29mm 40 50 44 28 71 180 13

120 Roll 6 x 6cm

(2-1/4 X 2-1/4 in.) 85 75 59 47 84 270 18

120 Roll 6 x 7cm

(2-1/4 X 2-3/4 in.) 92 90 54 58 77 180 29

120 Roll 5.4 x 7.9cm

(2-1/8 X 3-1/8 in.) 96 100 51 47 91 180 30

Polaroid Pack 9x 10.8cm

(3-1/4 X 4-1/4 in.) 140 135 55 NA NA NA NA

4x5 Sheet 9.5 x 12cm

(3-3/4 X 4-3/4 in.) 153 165 50 90 81 375 23

8 X 10 Sheet 19.7 x 25.8cm

(7.3/4 X 9-3/4 in.) 325 300 57 240 68 480 37
acteristic is that the distance from the front of the lens to the film is much less than the focal length of the lens; that is, it gives a long focal length in a short lens. The term telephoto

should be restricted to lenses of this type, and

the term "tele-lens" or long-focus lens used as

the general term for lenses used to provide

large images of distant subjects. Coverage

ratios for tele-lenses will be small, from about

0.5 to 0.05 or less.

Long focus lenses are normally listed by focal

length, but are selected on the basis of the relative magnification they provide. Relative magnification is computed with respect to the normal

focal length lens for a particular picture size. A

50 mm lens is normal for a 35 mm single lens

reflex camera. If we replace the normal lens by a 300 mm lens, the magnification is 300/50 or 6 times. A 16 mm camera has a normal lens of 25 mm focal length. The same 300 mm lens on

the 16 mm camera provides a magnification of 300/25 or 12 times. A lens of this focal length

might well be a telephoto type.

There is a very wide selection of long-focus

lenses available today. These are very useful in surveillance photography, in which image size is of crucial importance. However, while all 300 mm lenses, for example, provide the same

image size regardless of the camera with which

they are used, they may not be equally suitable

because of the large magnification to which sur- veillance negatives are normally subjected. A

300 mm lens for a 20 x 25 cm (8 x 10 in) view camera is designed to have a wide angular

coverage, and this may involve a sacrifice of pic- ture sharpness near the center of the field. Such a lens would produce results inferior to those of a 300 mm lens designed for use on a

single lens reflex with maximum center

resolution. The only simple way to tell whether

the large format lens is usable is to test the two

lenses on the same subject. In general, the lens

designed for the smaller negative size will provide the higher quality picture, in lenses of equal focal length and aperture.

Lens design and manufacture is a series of compromises. Invariably, many of the characteristics

which are desired in a lens have conflicting re- quirements: one can only be obtained by

sacrificing another. Speed is obtained at the

sacrifice of angular coverage and overall image

quality. The ability to work in both visual and

infrared light without refocusing the lens is obtained at the expense of simplicity of design,

by using many elements of more expensive

glass and by reducing maximum lens aperture.

Maximum resolution, as required for microfilming, is obtained by designing lenses

that work well for only a very limited range of subject distances. Therefore, most lenses are designed with some specific and limited type of use in mind.

The normal camera lens is designed to work at distances from infinity to about 10 focal lengths

from the subject, in daylight. Its performance is invariably improved by stopping down to a

smaller than maximum aperture. Many general

purpose lenses suffer noticeable deterioration

when used in infrared light (which is important

to the law enforcement photographer) and most

lenses must be refocused in infrared. A special

focus mark is provided on many lenses for infrared illumination. If it is not present, increase

the lens to film distance, after visual focusing,

by about 5 percent of the focal length of the

lens and make tests about this point to determine the position giving the sharpest

image.
Within its limits, a high quality general purpose

photographic lens will provide more detail in its image than the average film can record. For

certain special subjects, however, special

lenses should be used. These are listed below

in the order of their importance.

Enlarging Lenses

A general purpose lens produces an image

which is not flat when the subject is flat; the

edge of the image curves in toward the lens. In enlarging, we have a flat negative as a subject,

and the image is on a flat paper surface. Both

subject and image are also very close to the

lens. Both conditions cause a deterioration of the final image. The remedy is to use an

enlarging lens, which is designed to have a very

flat field and to work at distances from the

paper of 2 to 10 focal lengths. A high quality

enlarging lens will also be color corrected to work with tungsten light, which has much more

red than daylight.

Macro Lenses

The law enforcement photographer frequently

needs to get large images of small objects: fin- gerprints, handwriting, tool marks, etc. His subject distance will be very much less than 10

focal lengths. While some general purpose

lenses work well under these conditions, many

are completely useless; only careful tests will

tell how well a given general purpose lens can

form an image of a very close subject. A macro

lens is specifically designed to provide sharp

images of subjects at distances that approach one focal length. When used with bellows or extension tube, macro lenses can produce

images that are several times the size of the

subject.

Macro lenses have other unusual properties; as

the image size approaches that of the subject, a

dividing line is approached where the normal

photographic rules change. As long as the

image is smaller than the subject, long-focus

lenses provide larger images of the subject, and

short-focus lenses have more depth of field than long-focus lenses.

When the image that is formed becomes larger

than the subject, however, the rules reverse. For larger than actual size images, short-focus

lenses produce larger images for a given lensto-film distance than long-focus lenses, and

long-focus lenses have more depth of field than

short-focus lenses. There is no sudden reversal

of the rules; rather, the trends that have

governed image behavior when the image is smaller than the subject become less well defined, then start increasing in the opposite di- rection.

The use of a copy camera is a good example.

For images of less than actual size, the normal

procedure is to keep the film and subject fixed

and move the lens to focus the image. This

becomes more and more difficult as the one-to- one ratio is approached. At one-to-one, moving

the lens merely changes the image size with

little change of focus; focusing must be done by

moving the subject or the film instead of the

lens. For images much larger than actual size, it becomes necessary to keep the lens and film stationary and move the subject to focus, since

under these conditions a change in lens to film distance changes the focus slowly and the

image size rapidly.

Process and Copy Lenses

The process lens has much in common with the

enlarging lens, although it is intended for use in a camera as opposed to an enlarger. It might be

considered a superior enlarging lens. It is designed specifically for use at a one-to-one

magnification and normally performs well at magnifications of from ten-to-one to one-to-ten.

It is a much slower lens than an enlarging lens,

the usual speed being f/8, and is generally of much longer focal length, 500 mm to 1000 mm

being common. In the process lens, speed and

angular coverage have been sacrificed in order

to gain maximum resolution over the full field of the lens, and over a large wavelength range. The process lens is the basic lens for all color

separation work; it must be capable of making

negatives through three different color filters (red, blue and green) and producing three

separate black and white images of exactly the

same size. This requires better color correction
than is necessary for any other photographic

purpose. Where a fixed copy camera is set up

for document reproduction of all types, the

process lens is the best choice for producing

the highest quality work.

Zoom or Variable Focus Lenses

This type of lens is a relative newcomer to the

photographic field. The modern zoom lens has

been made possible by two developments: the

electronic computer, which made practical the

design of complex systems with the 12 to 20 or more elements required for the zoom lens, and

the lens coating, which made it possible for lens

designs with large numbers of elements to produce crisp, high-contrast images. From this combination came, first, heavy and

cumbersome zoom lenses for television cameras. The technique was then extended to 16 mm and 8 mm movie camera lenses. Today,

the zoom lens is the standard and only lens on most of the Super-8 movie cameras for non-professional use. In the 35 mm single lens reflex

field, the zoom lens has become a standard

accessory lens for a large proportion of all the camera systems available. While zoom lenses

are common in the three fields of television,

motion pictures and still photography, the re- quirements in each field are quite different.

Still pictures require the maximum resolution

and sharpness. While slight variations in focus

with change in focal length can be tolerated,

since focusing can always be done after focal

length is selected, the resulting negative must

be comparable in contrast, sharpness and

resolution with those produced by the best of the fixed focal length lenses. In addition, the

lens speed must be high; the 35 mm zoom lens

must have an aperture of at least f/3.5 for the

lens to be competitive. Size and weight must be

kept to a minimum.

In the motion picture field, the overall picture

quality requirements are as high as for the

35 mm single lens reflex, but this problem is somewhat simplified because of the shorter

focal lengths involved. For motion picture and

TV work, however, it is essential that the lens

remain in perfect focus as the focal length is changed; without this, the zoom shot becomes

impossible. It was the zoom shot, with many of the attributes of the dolly shot and none of the

difficulty in performing it, that inspired the development of the modern zoom lens. In the TV

zoom lens, resolution is not as important as in

still and movie lenses, since the TV system has

a very limited resolution compared to film. Light

transmission and contrast are more important

for TV use.

For the law enforcement photographer, the

zoom lens has several advantages. It enables

him to choose his perspective and image size

independently. He can set up his camera where

he has to, or wants to, in order to obtain the

required perspective. A quick shift of the zoom

control, and the image size is adjusted to the

available film area. This should result in faster, more efficient picture taking, as well as pictures

that show just what is wanted, no more and no

less

A second advantage is found in those zoom

lenses that combine the variable focal length

zoom with the short distance performance of the macro lens. With only one lens, a much

wider range of assignments can be handled,

from accident scene, to long distance identifica- tion of a suspect, to full size images of wounds

and tool marks. The macro-zoom lens is constructed so that, in the zoom mode, a set of moving elements controls the lens focal length.

When shifted to the macro position, the focal length is fixed (generally at the short end of the

focal length range) and the same moving

elements now do the focusing and control the

lens aberrations so that the image is sharp even

though the subject is much closer than normal.

Since focal length range is the major attribute of the zoom lens, it is pertinent to mention some

of the available ranges. In the 16 mm movie

and TV field, a 10-to-1 focal length range has

become almost standard for professional work.

This is normally from 12 to 120 mm. Thus, one

lens covers the full range from extreme wide

angle to full telephoto.

In the 35 mm single lens reflex field, such

extreme ranges have not as yet been produced.

Those available start at 35 mm and go to ap- proximately 300 mm with a three-to-one overall
range. One or two manufacturers supply lenses

for their own cameras with a six-to-one range of 50 mm to 300 mm (the greatest focal length

range available) and 200 to 600 mm (the

longest focal lengths). The 50 to 135 mm range

is a very good combination for the law enforcement photographer, particularly in conjunction

with a separate 24 to 35 mm wide angle lens. One manufacturer combines a 50 to 125 mm

zoom lens with a 2X extender, which converts it to a 100 to 250 mm lens. The lens also

performs as a macro lens, providing images up

to one-to-one. This is a very practical combination. However, it must be noted that the zoom

lens will be larger and heavier than the

equivalent fixed focal length lens of the same

maximum focal length and aperture. Though the

zoom lens on a 35 mm single lens reflex is equivalent to a whole battery of single lenses, it also results in always carrying the largest and

heaviest of the group. It is not a cure-all.

When it comes to surveillance jobs, the zoom

lens will generally not be of long enough focal length for the really tough assignments, and a

truly long fixed focal length lens (500 mm or more) will probably be required. A good criterion

is to use at least one millimeter of focal length

for every foot between the subject and the camera in order to get a recognizable identification shot. Two millimeters per foot will guarantee

results, from the focal length standpoint. For lenses of such extreme focal length, every other

requirement, except lens speed, is subordinated

to image size. A few manufacturers have

concentrated on this field, but the selection is meager compared to that available below

500 mm. The laws of optics prevent any lens

with a focal length of more than 500 mm and a reasonable aperture from being anything but

large, heavy and expensive. For problems of

this type, there are three aids for the equipment

selector: tele-extenders, catadioptric lenses and

telescopes.
Tele-Extenders

A tele-extender is a type of auxiliary lens that is produced by many manufacturers. It is used

between a regular lens and the camera to increase the focal length of the regular lens by a factor of two or three. Where there is an

occasional need for an extra-long focal length

lens, this is probably the best solution. All extenders degrade the quality of the image to some extent. They also increase the f-number

of the lens by the same factor by which they

increase the focal length: an f/4 lens becomes

an f/8 when used with a 2X extender. Some

extenders are specifically designed for use with

particular lenses and, in general, these can be

expected to give the best quality images. Since

the results with different extenders differ greatly,

and cannot be predicted, the only remedy is to take test pictures with your own equipment

before buying one.

Reflecting or Catadloptric Lenses

There is a fairly good selection of special longfocus lenses of the catadloptric type. These are combinations of lenses and mirrors, used to produce effects that cannot be obtained by

lenses alone. Their focal lengths are normally

500 mm or more. These lenses are noted for

their extremely small size as compared to their focal length. As focal lengths increase,

catadloptric lenses in general are capable of producing sharper and higher quality pictures

than the equivalent conventional lenses. A

1000 mm catadloptric lens may be no longer

than a 200 mm conventional lens resulting in a

relatively small and compact long focus camera

system. Such lenses, however, do not have the

conventional adjustable aperture, and the availa- ble f-stops are limited.

Telescopes

A useful alternative, where a focal length of more than 1000 mm is required, is to use some

form of telescope or spotting scope in place of the photographic lens. Each type of scope has

its own problems and will have to be considered on its own special merits. One greatly respected

astronomical telescope (the Questar) is avail- able in a model which has been modified for use with a single lens reflex 35 mm camera for

strictly photographic use. The telescope and camera combined are less than 16 inches long,

and provide a focal length of 1400 mm or more, depending on the extension tubes used. The

total system is very convenient to use.

3v
I
EXPOSURE

METERS

Use of exposure meters can insure the photographer of consistent proper exposure

under many conditions.

39
EXPOSURE METERS

An exposure meter of some type is an essential

part of the working kit of every law enforcement

photographer. With it, the photographer measures the illumination coming from the subject and entering the camera lens. For every

lens aperture and film speed, there is a unique

product of illumination and time in seconds that represents the total amount of light required to produce the optimum density in the developed

film. The exposure meter measures the illumination, and the calculator into which the ASA film speed has been entered is used to compute the

length of time the light from each lens aperture

must be allowed to act.

Exposure meters as separate units are not as

important as they once were because of the

widespread use of cameras with built-in meters

and automatic exposure controls. The essential

principles of operation and use are, however,

the same for separate meters and built-in meters.

Separate exposure meters are of two general

types: incident light and reflected light. Built-in exposure meters of the types normally used in single lens reflex cameras are almost universally of the reflected-light type. A third type of meter, which is found less frequently, is the spot

meter. It too is found as both a separate and a

built-in meter. The integrating or flash meter is another type.

The reflected-light meter, which was the first of the electric exposure meters to be used and is

still the most commonly encountered, is simple

in principle. A photoelectric cell (photocell) is placed in a position near the camera lens and

arranged to receive light from about the same

angle as an "average" camera lens. Two types

of photocells may be used with all types of exposure meters. One type, the photovoltaic, (barrier

layer) directly converts the light into an electri- cal current which is measured by a sensitive

ammeter. The amount of the current is directly

proportional to the brightness of the light. This

type of cell has the advantage of not requiring

any battery, but its ability to measure weak or dim light is limited. The second type, the photoconductive photocell, has a resistance that is inversely proportional to the illumination falling on it. A miniature battery is used to provide the source of electric current. The photocell

controls the current, which is measured on a

sensitive ammeter. This type of photocell has

the advantage of being very much smaller than

the barrier layer cell and very much more

sensitive to dim light. The most commonly used

photocell of this type is the cadmium sulphide,

or CdS, cell. Silicon photodiodes, which provide a greater sensitivity to changing light levels, are

replacing the CdS cell, and more recently, some

manufacturers have started to use gallium

arsenide-phosphide (GAsP) cells, which are the

most sensitive of the photocells presently avail- able.

The reflected-light meter has the following advantages: it is small, rugged, relatively inexpensive, and requires no upkeep if of the barrier layer type; can be used from the camera

position; can be filtered to see colors in about

the same relations as the film sees them; and

has a reasonably long life.

Its disadvantages are: its field of view should

match that of the camera lens but is generally

larger; it is influenced too much by small areas

of bright illumination in the subject, tending to expose for the brightest area and underexpose

much darker ones; it is unduly influenced by the

overall lightness or darkness of the subject,

tending to expose so as to offset these

differences; while it looks at a subject from the

same position as the camera lens, it does not respond to light in the same fashion as the lensfilm combination. Some type of shield or baffle

is essential in order to limit the light reaching

the cell to that coming from the same direction as that reaching the film through the camera
lens. Because of the way in which the cell responds to light, this is difficult to do

regardless of whether the barrier layer or the

CdS cell is used.

The incident-light meter uses a different approach. It looks at the light which is reaching

the subject from all directions. The meter faces

toward the light source and infers the proper ex- posure from this light. It too, uses either type of photocell.

The advantages of the incident-light meter are:

it tends to record all parts of the subject at density levels which correspond to their relative brightnesses; it is not affected by the proportion

of light to dark areas in the subject, but only the

brightness of the light falling on the subject; it is more useful in very dim illumination, since it measures the total incident illumination, which is always more than the reflected illumination.

The disadvantages of the incident-light meter

are: it should be used from the subject position,

with the meter facing toward the camera; it is not generally usable for subjects which are themselves luminous, but only with those that are luminous because they reflect light which is falling on them from an external source.

Many of the available professional meters are designed for use with either reflected light or

incident light. This is the ideal system, since it provides maximum flexibility for use under

unusual conditions: the consistency of the

incident-light meter and the ability of the

reflected-light meter to deal with self-luminous

subjects.

A third type of exposure meter is the spot

meter. It is basically a reflected-light meter

which has been placed behind a telescope so

that the sensing photocell sees only a very tiny area of the subject. Each small element of the

subject can have its brightness measured

directly by the meter from the camera position.

The advantages of the spot meter are: it sees and responds to each spot in the subject in the same way that the corresponding area of the

film in the camera does; it can be used from the camera position to measure exposure on

inaccessible subjects; and it is ideal for

measuring exposure for extreme long-focus

lenses, since it sees only what the lens sees.

The disadvantages of the spot meter are: it is time consuming to use, since many points on

the subject must be read and the exposure is computed from the brightest and darkest

elements of major importance; it is larger and more expensive than either the incident or

reflected-light meters; and it requires more

judgment on the part of the user.

There is a fourth type of exposure meter,

originally used in photomicrography but

currently found in a modified form in most single

lens reflex cameras with built-in exposure

control. This meter has the high sensitivity to dim light provided by the photoconductor, the

small area reading capabilities of the spot

meter, and much of the tolerance of the incident

type meter for bright subject areas. In photomicrography, a probe-type of exposure

meter with a very small photocell is used to measure the brightness of the image directly in the film plane of the camera. The same

principle is used in the single lens reflex camera

having a through-the-lens metering system. This uses one or more photocells, placed in the

optical system so that they measure the

brightness of the image on the viewing screen. Two types of adjusting system are used. In the

stop-down manual system, there is no

connection between the lens diaphragm and

the exposure meter. The lens is stopped down

manually until the meter indicator is centered.

The image is then the right brightness on the

viewing screen and the lens is at the proper ap-
erture for taking the picture. This system can be

used with any lens on the camera, since

diaphragm coupling is unnecessary. However, it forces the photographer to always work with a stopped-down image on the viewing screen, which may give problems in poor light. The alternate system, which requires mechanical coupling between the lens diaphragm

control and the meter, is the one more commonly used. As the diaphragm control on

the lens is operated to adjust the exposure

meter indicator, the lens is not actually stopped

down, but the corresponding stop is preset into the system. The meter is adjusted simultaneously with the diaphragm control and so

reflects the preset stop in its reading. When the

exposure release is operated, the lens is automatically stopped down to the preset point

before the exposure is actually made. Many

single lens reflex cameras are arranged so that

either method can be used.

Either method has the advantage that it compensates for bellows extension on close-up

shots; for variations in diaphragm calibration

from lens to lens; for variations in lens

transmittance; and for filters placed over the

lens. Either method eliminates the hypersensitivity to bright light sources just outside the

field-of-view of the lens, which is characteristic

of photocells external to the main lens. Both

through-the-lens systems are quite sensitive to feed-back of stray light through the eyepiece of the viewing system. The stop-down method is more prone to trouble since it is always working

with a lower light level at the sensor.

The through-the-lens exposure system normally uses two or more photocells, which are so

positioned that each views a limited area of the scene. Their relative effects on the camera ex- posure are balanced for the best overall result. Generally, the center portion of the picture area has more effect on exposure than the outer borders have.

Another type of through-the-lens system in use has a single photocell positioned on the lens

axis, a small distance away from the film plane.

This gives a center-weighted exposure

determination. The cell is retracted from its position as the shutter release is operated.

Exposure meters using CdS detectors are accurate over a broad range of illumination

levels; however, they suffer a loss of sensitivity at low light levels immediately following use

under conditions of bright illumination. The CdS

detector will slowly recover full low light level sensitivity over a period of many minutes, but

may not provide correct exposures if one takes

pictures outdoors and immediately attempts to use the detector in a dimly lighted interior. Several manufacturers have introduced cameras that replace the CdS detectors with silicon photodiodes or gallium arsenide-phosphide

cells, both of which are much more sensitive

than the CdS detector and retain low light level

sensitivity even after use in bright light. A relatively new development in the exposure

meter field is the integrating or flash exposure

meter. These were made practical for normal use by the miniaturization and low power requirements of solid-state electronic modules, which

reduced the size of the unit from a laboratory

instrument to a pocket meter.

The unit senses any sudden increase in light

and measures both brightness and duration, even when the latter is only a few microseconds. The product of the two, which is the total exposure, is then displayed on a meter. With

this type of meter, the photographer can make

a flash lighting setup containing several differ- ent sources fired by slave units from a master

flash lamp and predetermine whether his exposure is correct or not, something that had not

previously been practical. Meters of this type measure the reflected light received at the camera from the full subject for the full duration of the flash. Some other types of exposure sensing systems

are in use, such as photocells around, but

external to the lens, and photocells built into the

reflex mirror as part of the coating which

reflects the light to the viewing screen. While

there are some advantages and disadvantages

to each different system, all are capable of providing good results. Some are more forgiving of one type of error and some of another. A

little experience with any one of them will allow

the photographer to learn their individual idiosyncrasies and obtain consistent exposures

under many conditions.

FILM

Film available for the use of the law enforcement photographer varies widely in size, speed,

color sensitivity, grain, resolution, contrast, maximum density and sensitivity to handling, as well as in how it is packaged for different types of cameras, and whether it is processed by conventional photographic methods or is of the

instant process type.

For this guide, we have basically considered

both equipment and film as being in three

general size categories: small, medium and

large. Film sizes 35 mm wide and under fall in the small category. Films from 35 mm to 90 mm fall in the medium size category. Any

film larger than 90 mm has arbitrarily been

placed in the large category. In the small size are found sub-miniature cameras and 35 mm

cameras with picture sizes of 24 x 36 mm. In the medium size category are found a collection

of cameras taking pictures 6 x 4.5 cm

(21/4x1 5/8), 6 X 6 cm (21/4x21/4 in), 6 X 7 cm (2 1/4 X 2 3/4 in) and 6 x 8 cm

(2 1/4x3 1/4 in), plus a few odd sizes (mostly

instant process). In the large size are found

8 X 10.8 cm (3 1/4 X 4 1/4 in) (mostly instant

process), 10 x 12.5 cm (4x5 in) and

20 X 25 cm (8 X 10 in) pictures.

The 20 X 25 cm (8x10 in) print will be

considered the standard picture size toward

which all law enforcement photography is aimed. This will be true for the majority of pic- tures intended for formal court presentation and

it is the preferred size for many other purposes.

It will not be true, however, for pictures from

specialized systems used for making personnel

identification photos, for some fingerprint

photos, and for some surveillance pictures

where picture size may be determined by how

much enlargment the negative can stand.

With reference to their classification as large,

medium and small, negatives will require the

following amounts of linear enlargement to

make 20 x 25 cm (8x10 in) prints: large size

negatives, from zero to three times; medium

size negatives, from three to eight times; and

small size negatives, more than eight times. The

division between medium and small negatives

falls at a critical point in the recording capability

of photographic material. The result is the re- quirement for a major change in total photographic technique when the shift is made from

medium to small size negatives. The dividing

line between the two techniques is not abrupt or

rigid, but the personnel responsible for selecting

equipment that will determine the picture size

used for various purposes should be aware that the decision is not to simply "make the print

larger." Small negatives can and do produce

excellent prints even larger than 20 x 25 cm

(8x10 in). They do not do so as consistently

or with the same lack of care and attention to

detail at every stage in lighting, exposing, pro- cessing and printing the final picture, as can be

done with medium or large negatives. This is a

fact of life due to the basic nature of the photographic process.

Experience and tests have shown that a photographic print will appear crisp and sharp to the

observer only under certain conditions. One of these conditions is the fineness of the detail it contains. Detail finer than about 1/20 of a milli- meter (that is, 10 line pairs per millimeter) will not contribute to its apparent quality. If the

finest detail is coarser than this, the observer can tell that the quality has been lowered. Slow

and medium speed films can record well over 100 line pairs per millimeter when used with

ordinary lenses, and at apertures several stops

smaller than maximum. High speed films have

lower capabilities; even under ideal conditions,

80 line pairs per millimeter is seldom reached.

Dividing the line pairs per millimeter in the negative by the required line pairs per millimeter in the print gives us the maximum number of times

the negative can be enlarged before the

deterioration in print quality, due to lack of detail
in the negative, becomes noticeable. With the

fast or medium speed films, under any condition

other than ideal, a 50-line pair per millimeter

resolution is a reasonable expectation. This sets the maximum enlargement at five times, which means a 12.5 x 18 cm (5x7 in) print from a 35 mm negative, before quality starts to drop. A

6 X 6 cm (2 1/4 X 2 1/4 in) negative, under

identical conditions will give a 28 x 28 cm

(11 X 1 1 in) print, which means we can crop off part of the negative and still get a 20 x 25 cm

(8x10 in) print with good detail.

The guidelines given above must not be taken as hard and fast numbers. A seven times en- largement from one negative may look good,

while the duplicate shot next to it on the roll may look very bad. Obviously, something

happened to make the two different, but determining what it was and preventing it from

happening again may be impossible tasks. The

generalities drawn will be found valid in practice. They should be given proper consideration in determining the film size that will form

the foundation for photography in any law en- forcement operation.

Packaging

Film is packaged differently for use with differ- ent cameras. Six different types of packaging

are commonly encountered.

Roll Film. This consists of long strips of film, normally for eight to twelve exposures, backed

by a slightly wider strip of light-proof paper, marked with exposure numbers to provide the

proper spacing between frames, and rolled onto a light-tight spool which can be loaded into a camera in daylight.

Bulk Film. This consists of carefully slit widths of

film of various dimensions, similar to roll film but

minus the backing paper. Generally supplied in lengths of 100 feet or more in light-proof

wrappings. It must be manually loaded into the camera or some form of cartridge or magazine,

in total darkness, before it can be used. Bulk

film includes motion picture film, which is normally on a flanged spool which is proof

against subdued light and is provided with

sufficient extra film on the roll (generally about

10 feet) to serve as a leader and trailer to protect the main portion of the film from being

fogged during the process of loading into a

16 mm camera.

Film Cartridge. This is the standard packaging

for film for 35 mm still cameras. A length of 35 mm wide, perforated motion picture film, sufficiently long for 20 or 36 exposures of 24 X 36 mm size, is wound on a standard size

spool, and inserted in a metal magazine

provided with a velvet lined slit through which

the end of the film is extended. The magazine

dimensions are standardized and the loaded
magazine is light-tight in direct sunlight. The

protruding end of the film strip is fastened to the camera take-up spool, and the film transferred

to this spool during picture taking. After exposure, the film must be manually rewound back

into the magazine before the camera can be

opened and the film removed.

Instant Load Cartridge. This consists of two film magazines (one for unexposed, one for exposed film), connected by a film gate or aperture which guides and locates the film. Since

the film is already attached to the take-up spool,

there is no film threading or rewinding involved

in using the instant load cartridge. The cartridge

is shaped so that it can only be inserted in the camera in one way. Inserting it automatically

adjusts the camera exposure mechanism to the

proper speed setting for the type of film contained in the cartridge. When the last exposure is made and the film advanced to the end,

the camera can be immediately opened and the

film removed without rewinding. Instant load car- tridges are available in three sizes: 126 size car- tridges for 29 X 32 mm picture size instant load cameras; 110 size cartridges for sub-miniature

instant-load cameras; and Super-8 mm motion

picture camera cartridges of 50 feet.

Sheet Film. This is packaged in light-proof

packages containing a specified number of accurately cut sheets of heavy base film, notch

coded in the upper right hand corner of the

sheet (when facing the emulsion side and the

film is vertical) for easy identification of film type

and emulsion orientation. Individual sheets are manually removed from the packing in total darkness, and loaded into individual sheet film holders containing two sheets of film, back to back, separated by a divider. The holders are closed with opaque slides, after which they can

be handled in full daylight, inserted individually

into view or press type cameras and one slide removed for exposure. The slide is replaced in the reverse position to indicate exposure and

the holder either reversed for exposure of the

second film or returned to the darkroom for pro- cessing. Sheet film is commonly found only in sizes 6 x 8 cm (2 1/4 X 3 1/4 in), 8 x 10.8 cm

(3 1/4x4 1/4 in), 10 x 12.5 cm (4 x 5 in), 12.5 x 18 cm (5 x 7 in), and 20 x 25 cm (8 x 10 in).

Film Pack. This is used instead of sheet film when many pictures have to be made in rapid

succession. A film pack consists of a stack of thin-base sheet films loaded in a metal frame

with opaque black paper over the top sheet and

between films. A long paper tab is fastened to the bottom of each sheet. When the first tab is pulled, the front safety cover is removed from

the stack. After the front film of the stack is exposed, its paper tab is pulled, transporting the

film from the position in the front of the stack,

emulsion facing the lens, around the bottom

end of the stack and into the back with the

emulsion facing away from the lens. A flat spring divider, originally pushing the entire stack

to the front of the film pack frame, is now

between the exposed and unexposed sections,

pressing the unexposed sheets fon^/ard to register with the front of the pack frame. The

films are then exposed in sequence. Film packs

are highly convenient in the small sizes and

provide a large exposure capacity in a very

small space. Both fully exposed and unexposed

packs can be placed in a film pack adapter in daylight. The adapter is placed in the camera

and used exactly like a sheet film holder. Pack

film must be made on a thin base, to allow for the sharp bend in the reversing operation when

the tab is pulled. This makes pack film, in the

10 X 12.5 cm (4 X 5 in) and larger sizes, highly

subject to film buckling, sometimes causing

local out-of-focus patches in the negative.

Increased cost per exposure (as compared to sheet film) is another disadvantage that must be

considered.

Film Speed

An important characteristic of film is film speed.

This is a measure of how much light must be

allowed to act on the film in order to record a

picture. For a given level of illumination on the

subject and a given lens aperture, the higher

the film speed, the shorter the exposure

required. However, high speed in film can only

be obtained at a price: a very significant loss in the film's ability to record fine detail and a great

increase in the grain size. Grain is a characteristic, overall mottled appearance in the emulsion

forming the photographic image. A fine-grain

film can have its image enlarged many times
before grain becomes apparent to the eye, while a high-speed film may have its grain

apparent to the eye with no enlargement. The

coarse-grain film has to be used only in large

negatives or serious limitations on maximum

acceptable enlargement must be accepted. It is not likely to produce a good print from a 35 mm

camera, whose negative must be enlarged eight or more times to get a 20 x 25 cm (8 x 10 in) picture.

Grain is a function of exposure and development as well as of film type. In general, overex- posure and underdevelopment tend to decrease

grain size. Fine grain developers reduce grain

size, sometimes at some sacrifice of film speed.

Excess soaking in processing solutions, and

higher temperature processing solutions,

contribute to increased graininess.

Since films are available in a wide range of speeds, a medium-speed film is generally the

best choice for all around use. High-speed films are best reserved for those jobs where any pic- ture is better than none and tests have shown

that medium-speed films produce no picture.

The smaller the area of the negative to be used

for the print, the more careful one must be to minimize grain. Speed ratings range from ASA 8

for slow process films, to ASA 4000 for extremely fast surveillance films.

It should be noted that the effective film speed

which can be obtained on any emulsion is subject to some control by the amount of development given and the type of developer used.

This variation, for a given emulsion, is normally

less than the variation between a medium

speed film and high speed film.

Color Sensitivity

A characteristic of all black and white films is their varying sensitivity to light of different colors. Film is available in three major types of color sensitivity: color blind or blue sensitive

film; orthochromatic or blue and green sensitive

film; and panchromatic or blue-green-red (all- color) sensitive film. Blue sensitive films will show objects that are bright red to the eye as

black in the print. Orthochromatic films will show blue and green objects in shades of gray

that are similar to their visual appearance, but

red objects will still be much too dark. Panchromatic films tend to show all colors in rel- ative shades of gray that match their relative brightness to the eye. The majority of black and

white film used in law enforcement today is panchromatic and it is best for general use. However, where large amounts of one type of work are being done, the use of one of the

other types of film may offer advantages.

All manufacturers issue specification sheets for each of the films which they manufacture.

These sheets list the film characteristics, give correct processing times and formulas, and list the type of subject for which the film is specially

suited.

COLOR FILIVIS

The films so far considered have been the

normal black and white negative type. Color

films must also be considered.

Packaging. All color films are packaged in exactly the same manner as are black and

white films. The selection of sizes is more

limited and not all types of color film are avail- able in all of the common sizes. Some color negative materials are available in a very limited size range.

Film Speed. Color films in general are much

slower in speed than black and white films. Like

black and white films, however, the fastest color

films provide the poorest resolution and the

grainiest pictures. The rated speed of color films

will vary from about ASA 25 to about ASA 400.

Fidelity of color reproduction tends to decrease

as film speed goes up and is always sacrificed

when any color film is pushed. Pushing

(normally applied to reversal or positive color

film only) involves changes in processing

procedures which result in higher effective film speed ratings, at the expense of more grain

(often much more), poorer color rendition and

loss of overall quality in the transparency. It has

value when film is known to have been

underexposed one or at most two stops. It should be used as an emergency tool and not used consistently.
Types of Color Emulsions. Color films come in the form of positive or reversal emulsions and

color negative emulsions. All color films are very

complex, multiple layer emulsions, as compared

to the simple one to three layers found in black

and white films (anti-halation sub-coating, silver halide emulsion, plain gelatin over-coating).

Some black and white films have only the

essential silver halide emulsion layer.

Positive Color Films. All currently used color

films are multilayer films with a minimum of three separate light sensitive emulsions (plus

necessary filter and separation layers), each of which records one of the three primary colors

(for most emulsions red, green and blue). In any

emulsion, the image starts at the surface and

extends downward through the layer in proportion to the illumination at that point.

Development converts the image into a varying

thickness of metallic silver, like a relief map

upside down, backed by a complementary layer

having the same contour of undeveloped and

still light-sensitive silver emulsion under it, the

whole making up the thickness of the original

emulsion layer. In all reversal emulsions, this metallic silver negative image layer is chemically

bleached or removed. The remaining

complementary positive image is then re- exposed to light and developed to a positive

image. In a black and white reversal film, the

positive image is made insensitive to light and

washed. In color film, it is necessary to convert

the positive silver image into a color image

formed of colored dyes. And, in the color

reversal process, each of the three layers of the

film must be treated individually and converted

separately into differently colored dye images.

The complexity of the process and necessity for

strict control are evident.

In positive color films, variations in the compositions of the dyes and the compounds used to produce them cause variations in the "grain"

size of the dye and in the sharpness and

resolution of the resultant dye images. Higher

speed emulsions still tend to produce coarser

grained images. These are some of the

elements that determine the varying characteristics between color films of different types.

Color Negative Films. Color negative films are

similar in many respects to positive color films: they are multilayer in construction, start with

metallic silver images and end with color dye

images. The development process is carried

only to the point where the negative image layer

is obtained. Conversion from silver image to color image occurs at this point, but the colors

in the conversion are different. They are complementary to the actual colors of the

image at that point. A blue object becomes a

negative blue or yellow image. A green object

becomes a negative green or red image. There

are several advantages to the color negative.

Film speeds tend to be higher for a given

graininess and resolution. The negative process

is more forgiving of minor errors in exposure

than is the reversal process required for positives. Paper positive prints are made from

color negatives by direct printing on negative

color printing paper and the processing

procedure is simpler than the reversal processing procedure that must be followed when

making prints on positive color paper. Color negatives also make excellent black and white

prints, on a special panchromatic printing or enlarging paper. This is exposed and processed

in a manner identical to that for normal black

and white printing paper. Color negative

material would seem to have the best of both

worlds. Unfortunately, the color rendition in general has been inferior to that obtained with

the reversal processes.

As the process improves in overall quality, there

is certain to be a growing application in law en- forcement photography for the color negative

with its built-in capability for good black and

white prints without the need for a copy negative.

Instant Process Film

The Polaroid instant process black and white

film takes a picture, develops it, prints it and develops the print, in a single operation taking

about 15 seconds. Instant process film is packaged for use only in instant process cameras, in rolls, film packs, and single exposure

packets that fit a special developing holder that can be used with any 10 x 12.5 cm (4x5 in) press or view camera which takes standard size
film holders. Instant process film is available in

rolls, producing a picture size of 8 x 1 1 cm

(3 1/4x4 1/4 in), with ratings of ASA 200

(Type 42), ASA 3000 (Type 47), ASA 10,000

(Type 410), and high contrast (oscilloscope

recording). Film packs producing a picture size

of 8x11 cm (3 1 /4 X 4 1 /4 in) are available

with ratings of ASA 75 (Type 105) and ASA

3000 (Type 107). Single exposure packets are

available in the 10 x 12.5 cm (4x5 in) size

with film speeds of ASA 50 (Type 55 P/N), ASA

200 (Type 51), ASA 400 (Type 52), and ASA

3000 (Type 57). Types 105 and 55 P/N are a

positive-negative variety which produce a conventional black and white negative, plus a

positive paper print. The negative may be

discarded or cleared, washed and dried by conventional processing methods, after which it can be enlarged or printed like any other negative. Lantern slide transparency film is supplied in

rolls, ASA 200 (Type 146L) to make 8 x 10 cm

(31/4x4 in) lantern slides, and ASA 800

(Type 46L) to make 8x11 cm

(31/4x41/4 in) lantern slides.

Polaroid instant process film is also available in color positive or "Polacolor" form, each exposure producing one positive paper print. This

film has an ASA rating of 75. It is available in

rolls (Type 48) producing an image size of 8 X 11 cm (3 1/4x4 1/4 in); in film packs

(Type 88) size 8 x 8.5 cm (31/4x3 3/8 in) and (Type 1 08) size 8x11 cm

(3 1/4x4 1/4 in); in single exposure packets

(Type 58) size 10 x 12.5 cm (4 x 5 in); and SX70 which produces an image of 8 x 8 cm

(3 1/8x3 1/8 in). The instant process color

film is not quite as "instant" as the black and

white. The color requires 60 seconds for developing, but does not require cleaning and coating

after development, as does the black and white.

At the present time, Eastman Kodak manufactures a single instant process film, available

only in color, type PR 10. The picture area of

this film is 6 x 9 cm (2 1/2x3 1/2 in). The

film speed is ASA 150.

Storage

Photographic materials—film, paper and pro- cessing solutions—deteriorate with age. The

expiration dates given on film and paper apply

for storage at room temperature (not over 75

°F) Deterioration is greatly slowed by storage at low temperature (40 to 50 °F), as in a normal

refrigerator. Film so stored will show but slight

deterioration after several years of storage. Film

that has been refrigerated, however, should be

allowed to remain at room temperature in the

sealed container for about three hours before

use. Exposure to high temperatures will cause

rapid deterioration, particularly at temperature

above 90 °F.

Film and cameras should never be left in a car parked in the hot sun, particularly in the glove

compartment or the trunk. Exposed film may

deteriorate more rapidly than unexposed film, and color film may be more sensitive to high

temperatures than black and white film.

Summary

It is rather obvious at this point that no single

type of film will be best for all law enforcement

tasks. In most small departments two or three

types should be adequate. A medium speed

panchromatic, general purpose film which is available in all of the sizes that are used -should

be standardized as the major film and used

whenever possible. This gives the individual photographer the maximum amount of experience

with one emulsion, and is the best way for him
to learn what his film will and will not do. A

panchromatic process-type film will be of great

value where the material to be photographed

has very low contrast, such as faded photographs and printed matter, or primary

monochrome, like some fingerprints. Many

other uses for the process type of emulsion will be found. Proper choice of developer formulas

greatly broadens the contrast range that can be

covered, particularly in the direction of reduced

contrast by using soft working developers.

There will also be requirements for an extremely

high speed emulsion for surveillance and stakeouts. It would be worthwhile to make

comparative tests on a typical subject with at least two "ultra-speed" emulsions to determine

just how short an exposure can be used while

still getting usable prints. Practical, comparative

experiments of this type with different films and

developers will provide the best information to the photographer. When the technique is needed, it is at hand and proven.

The problem of color films versus black and

white and conventional versus instant process

films is complex. Easy answers may not be

readily available.

Color versus black and white should be decided on the requirements of the application. Color

photography is much more complex than black

and white. For many departments, use of color means that all color processing will be

contracted out. This means that processing

quality will probably be held to a more uniform

standard than when done in-house (in any but

the largest departments where a major effort can be justified to achieve processing control).

While quality can become more uniform under

these conditions, flexibility to cope with unusual

situations will be correspondingly lessened. It would appear that for many years to come black

and white photography will be a necessity in some form in almost all police departments.

Instant process versus conventional materials is relatively simple to answer. If professional photographic services are needed, both types of materials will be used, because there are places

where each excels. If photography is a secondary effort, to supplement other in-house

information, exclusive use of instant process

materials can be the right answer.

LIGHTING EQUIPMENT

The problem of providing supplementary lighting for taking law enforcement photographs has

always been a difficult one to solve. With equipment available today, the solution is getting

much simpler. Three basic types of supplementary lighting are available: electronic flash,

photoflash, and floodlights. What they will and

will not do, and where they are of greatest use,

will be considered.

The electronic flash lamp is the most convenient method, and it will solve most lighting

problems for still picture taking. The electronic or repeating flash gun is a relatively simple

device which has been available but not widely

used in photography for almost 40 years. One

of the many unglamorous beneficiaries of the

space program, it has developed into a

compact, inexpensive, light-weight, and very

powerful light source which now "tells itself what to do photographically."

In the electronic flash, a small battery provides

low voltage direct current electrical power,

which is fed into a storage tank or capacitor over a time period of 10 to 30 seconds, until the

capacitor is fully charged. This power is converted into light energy by discharging the

capacitor through a Xenon flash tube at the

instant the camera shutter is open. The Xenon

tube has the ability to very efficiently convert

the electrical energy stored by the capacitor into an extremely intense pulse of light (radiant

energy), and compress the conversion into an

extremely short time period.

The flash of light from the Xenon tube has

many desirable characteristics. It approximates

the color of daylight, so it works equally well with black and white and with color film. The

duration of the light is so short (about 1 /500 of a second at the very longest, to as short as 1/100,000 of a second) that there is little danger of any subject or camera motion

showing during the time the exposure is made.

Because of the small size of the Xenon tube, it

is simple to design very efficient reflectors to concentrate all of the light where it is needed in the field of the camera.

Electronic flash lamps are rated for the amount

of light they put out in several ways: in beam

candlepower-seconds, a direct measure of the

integrated output in light units; by the electrical input to the flash lamp in watt-seconds; by the

guide number of the system when used with film of a stated ASA speed rating; or by total light

output in lumen-seconds. The guide number,

provided in a table accompanying the unit, is the most meaningful to the photographer.

Dividing the guide number by the distance (in feet) from the flash lamp to the subject gives

the f-number required for correct exposure with a film of the stated ASA rating. Typical guide

numbers will be in the range from 25 to 50 or more for color film with an ASA rating of 25. At a 3 m (10 ft) distance, lens apertures will be

from f/2.5 to f/5.0. Convenient calculators are

often integral with the flash unit.

Electronic flash sources are compact, some

smaller than 35 mm cameras. They are light in weight, typically less than one pound, and have

a life of thousands of flashes. Three types of power sources are found: (1) Dry batteries of the standard flashlight type in the AA or A size. Typically, a set of batteries will give 100 flashes

in the higher powered units; more in the lower.

(2) Rechargeable nickel-cadmium (Ni-Cad)

battery packs of about the same size as the

flashlight battery pack. The Ni-Cad pack

normally gives fewer flashes per charge but can

be recharged hundreds of times. A charger

recharges the batteries when it is plugged into the 115 Volt ac line. (3) Converters that allow

operation directly from the ac power supply,

thus saving batteries where line power is avail- able. In some flash units, the battery charger serves also as a converter. Two different types of electronic flash lamps are now in use. The first, or manual, type takes a
fixed amount of charge from the batteries for every flash and uses it all. If more light is put out than is needed, the photographer has to stop down the lens to obtain the correct exposure. The second, or automatic, type varies the

duration of the flash to suit the needs of the situ- ation.

The first automatic electronic flash lamps used

a quenching circuit, controlled by a photocell sensor that measured the reflected light from

the subject. This type of circuit turns off the

flash lamp as soon as the correct amount of

light has been put on the subject, but continues

to drain the energy from the storage capacitor

until it is completely discharged.

The latest type is the thyristor-controlled electronic flash lamp. This is preset for the lens aperture to be used, in most cases with a choice

of two or more apertures. The flash unit is provided with a photocell sensor which measures the amount of light reflected back to the camera from the subject. It starts measuring

as soon as the flash comes on and, as soon as

the light has totaled up to the correct exposure

for the stop selected, the thyristor turns the

flash off, saving the balance of the energy that was stored in the capacitor. When the capacitor

recharges, only the actual amount of energy

used to take the picture is replaced, rather than

the whole amount needed to completely

recharge the capacitor. This makes for a great

saving in battery energy, so that many more

flashes per set of batteries (or per charge on

the rechargeable ones) are obtained. Pictures can be taken more rapidly, since it takes less time to charge the capacitor fully when it starts with a partial charge.

The major advantage of the automatic unit is that it greatly simplifies the problem of taking

pictures with flash illumination; exposure is automatically determined. This will be found

especially helpful when the photographer is using both flash and existing illumination. Balancing the two for a pleasing overall effect is simply a matter of selecting the desired aperture setting of the flash lamp, choosing a lens

aperture 1 or 1-1/2 stops smaller than this (to prevent the flash from completely overriding the

existing light) and setting the camera shutter

speed in the normal manner for the bright areas

of the picture. Other possibilities will suggest

themselves.

The traditional source of supplementary illumination is the photoflash lamp: a glass bulb, similar to an incandescent lamp bulb, filled with a measured amount of metal wire or shredded

metal foil in an atmosphere of pure oxygen. A

primer, which is fired by an electrical fuse,

ignites the wire or foil on command when the

shutter is operated. The foil burns with a brilliant
flash of light lasting about 1/25 of a second.

Photoflash lamps are often fired from "flash

guns." These are flashlight-type cases which

contain the battery for igniting the lamp, an

efficient reflector for controlling and directing

the light and a wire connecting the flash-lamp to the synchronizing circuit in the camera so that the flash goes off when the camera shutter is

fully open.

Electronic flash lamps fire instantly (within a few

microseconds) when their firing circuit is closed.

Photoflash lamps require an appreciable length

of time after the firing circuit is closed before

the illumination reaches its maximum value. The

delay varies with the type of bulb, ranging from

5 to 20 milliseconds. With photoflash lamps, the

firing circuit must be closed before the shutter

starts to open. Most camera synchronizing

circuits have two settings for this purpose: "X"

for electronic flash where the firing circuit is closed after the camera shutter is fully open;

"M" where the firing circuit is closed about 15

to 20 milliseconds before the shutter is fully

open. The correct setting must be made for the

type of illumination being used.

The big advantage of the photoflash bulb for the photographer who only occasionally needs

a few bulbs, but wants them ready to go without

prior preparation, is that the bulb has an

unlimited shelf life, and is a convenient, ever- ready source. For the high volume flash user, the main advantage is that the photoflash bulb

is a compact source of much more light than can be obtained from the electronic flash lamp.

In a small amount of space, enough lighting can

be stored to properly illuminate fairly large

outdoor areas, such as accident and crime scenes. The guide numbers for photoflash bulbs

used with ASA 25 color film are typically 40 to 50 for even small bulbs, such as the AG-IB,

and exceed 100 for the large "press" bulbs.

Those who use instant process or other cameras that are designed to use the smaller

photoflash bulbs will quickly find that it is not

possible to fully illuminate a large area, such as

the scene of a night time traffic accident, for in order to get all of the area of interest into the

field of view, it is necessary to stand so far away from the subject that insufficient light

reaches the scene. Adaptors are available to

allow the use of other "flash guns" designed for larger photoflash bulbs, or electronic flash lamp

units. Even with flash equipment that provides more illumination, it may still not be possible to illuminate the entire scene. When necessary,

two people working together can cover quite

large areas, "painting" the entire scene with

light. One person operates the camera on a

tripod, shutter set on bulb, opening the shutter

momentarily on command. The other, using the

battery-powered "flashgun" unit and a supply of the larger size bulbs, or an electronic flashlamp,

systematically covers the entire scene, breaking

it up into areas and firing a properly directed

light in each area, being careful to keep the il- lumination away from himself. The technique is simple, easily mastered, and very adaptable. A

dozen bulbs or flashes from an electronic flash- lamp can illuminate a large area.

Most press-type cameras are provided with

some form of photoflash lighting unit. Separate

photoflash "guns" are available in both press

and miniature types and can be adapted to any camera provided with synchronizer contacts. All currently available cameras are so provided.

A number of years ago, the photoflood lamp

came on the photographic scene and "cast

light" on many of the problems of both still and

motion picture photographers. This was a

simple low voltage incandescent lamp which was over-volted to produce a very large amount

of light. It traded lamp life for light and lasted

about two hours in continuous operation. The

tungsten-halogen (also known as quartz-iodine)

lamp has performed a similar revolution. It has

provided even more light from the same amount

of electrical power than the photoflood, at a

color temperature that more nearly approaches

daylight, and with a constant color temperature

and light output over the full life of the lamp.

The photoflood bulb is large and requires much

ventilation and large reflectors. The tungstenhalogen lamp is very small and its filament temperature is higher than that of other lamps.

Since more of its electrical input goes to produce light, it actually produces less total heat than the photoflood. Its small size makes it easier to cool and lends itself to the design of very efficient reflectors. Less of the bulb's light
gets lost and more gets on the subject where it

is wanted. The average life of quartz-halogen

bulbs is much greater than that of photoflood

bulbs, on the order of 50 hours rather than two

hours. Because of the limited life of both

photoflood. and tungsten-halogen lamps,

provision is generally made to operate the

lamps at a reduced voltage during the time

required to set up and focus the camera. The

voltage is then increased to the operating value

for the actual exposure. Lamp life is greatly

increased in this manner.

Where any volume of photography is done

which demands continuous light for setting up, posing, or photographing subjects, either still or movie, the law enforcement photographer will need tungsten-halogen or photoflood lamps as

light sources. They are the most compact,

efficient and portable continuous light sources

available. They provide the largest amount of

light per watt of electrical input or per cubic inch

of total size, of any continuous light source avail- able. Fluorescent lamps are more efficient but

bulkier, and may change the color balance.

The tungsten-halogen bulb works well at low

voltages. This has made possible continuous

light sources that provide a number of hours of illumination from portable battery packs. These

can be used for lighting small areas in locations

where no electrical power is available, particularly if movies are required.

The law enforcement photographer will require a standardized set-up of lights for personnel

identification photographs, preferably in a fixed

location where lighting and camera can be left ready to use at a moment's notice.

If much physical evidence photography is to be

done, other than at the scene of the crime, a much more complete lighting set-up with lights

selected from the standard units widely used by

commercial photographers may be desirable.

This includes flood lights for providing an overall

level of illumination, spotlights for emphasizing

texture or lighting deep recesses, ring lights

which fit around a lens and provide shadowless

illumination, and reflectors for softening

shadows. Since lighting requirements are determined directly by the object to be photographed, it is probably best to start with a mini- mum selection and add to it as required. For

many law enforcement photographers, an electronic or photoflash lighting unit on the main camera with a second similar unit for side

lighting, a slave-switch to fire both of the flashes

together, plus two or three small tungstenhalogen or photofloods in diffuse reflectors will cover all of the lighting requirements for many

assignments.
Ill,

FILTERS AND OTHER ACCESSORIES

The line of accessories available to the law en- forcement photographer is nearly endless. The

most important (filters, tripods, and copy stands)

will be described in some detail. Other, less important accessories will be listed to remind the

reader that such equipment is available.

Filters are relatively simple but very necessary

tools. Every law enforcement photographer will need a reasonable selection of them.

Filters are of two constructions: solid glass,

ground and polished, into which the necessary

color was incorporated when the glass was

originally fused; and thin sheets of gelatin

colored with dyes and cemented between

sheets of protective glass. Gelatin filters are not as commonly used as formerly because of the

greater variety of solid glass filters which is now

available. There are, however, many useful

filters that are obtainable only in gelatin. The

photographer should be familiar with both

varieties, and also with the fact that plain gelatin

films, in 2, 3 or 4 inch square sheets, can be

obtained very inexpensively and in more than

100 types. Because of their extreme thinness, a

gelatin filter can be used in front of or behind

most lenses without correction in focus. With

solid glass filters, the lens focus must be

readjusted when working at close distances

with the filter in front of the lens and will always

need adjustment if it is necessary to use the

filter behind the lens. Always focus the camera

with the filter in place, or test for accuracy of focus if the filter is too dark for visual focusing.

Five different types of filters will be found useful

in law enforcement work: contrast filters, color

correction filters (commonly called CC filters), polarizing filters, haze filters and neutral density

filters. Each has specific uses.

The underlying principle of the optical filter is rel- atively simple. Visible light is made up of energy

of all wavelengths between about 400 and 780

nanometers. While this is the range of wavelengths visible to the human eye, both

shorter and longer ones are of importance in photography, particularly those in the infrared

region between 780 and 900 nanometers. All filters pass light of some wavelengths and

absorb or reflect light of other wavelengths.

Filters are designated by what they absorb or

transmit. A high-pass filter transmits all wavelengths longer than a certain value. A lowpass filter transmits all wavelengths below a

given value. A neutral density filter transmits all wavelengths equally. A minus filter (minus blue,

for instance) absorbs the wavelengths

corresponding to the indicated color (blue). All

filters reflect or absorb some of the light that reaches them, even at the wavelengths they

pass, but they absorb a lot more of the incident

energy in the wavelengths they do not pass.

Filters are normally supplied in special screw-in

mounts that are designed to fit specific lenses.

"Series" size filters are circular, metal rimmed

filters designed for general use. The standard

sizes are series IV, V, VI, VII, and VIM. Adapter

rings are available that allow one set of filters to be used on a number of different size lenses.

Adapter rings are held in place on the lens by

friction and are simply pushed onto the lens. Step-up rings are available to fit small lens

adapter rings to allow the use of larger filter sizes, further increasing the interchangeability.

Contrast Filters

Contrast filters, which are the type most fre- quently needed in law enforcement work, are used to increase the apparent contrast in a subject. An example of this use is the copying of a

badly yellowed document written in sepia ink that has faded. With normal films, the document

is reproduced with very little contrast between

the writing and the paper, and it may be

illegible. By taking the picture through a filter
with the same color as the background (yellow),

we can increase the contrast. A deep yellow or a minus blue filter will normally lighten the

yellowed paper, making it photograph like a

clean white, and increase the contrast in the

final picture. Or we can go the opposite way

and use a filter that will hold back the parts of the picture which should be dark. For the sepia

ink, which is reddish, we use a minus red filter, which appears green. This will make the ink appear blacker, again increasing the contrast of the copy.

Every photographer doing document photography should have a selection of several densities

of filters in each of the major colors, red, yellow,

green and blue (see table 5). Filter selection can sometimes be made by visual inspection,

but actual test exposures will be necessary to

tell for certain what the overall effect is.

Color Compensating Filters

Color compensating filters are used in color photography. They are used with color film which

has been designed for use with one type of il- lumination, when it is desired to use it with a dif- ferent type of illumination. A commonly

encountered example is the salmon-colored

filter number 85A, used to allow tungsten light

balanced color film to be used in daylight. Each

Blue Green Red

Red Filter

different type of color film has its own filter re- quirements for conversion; filters for the same

general light conversion cannot necessarily be

used with different makes of film. A special series of CC filters is available to correct for small variations between the illumination for which a film was designed and that which must be used. These filters can, for example, be used to remove the excess blue

light present in daylight on a hazy day. The

filters are bluish or reddish in tint and very trans- parent, come in a wide variety of densities and

are also used in color printing and transparency

copying to achieve color fidelity in the final copy.

Table 5. GUIDE FOR

SELECTING

FILTERS FOR

MAXIMUM

CONTRAST

Choose filter color listed to render subject:

iqhtpr jtMtiiiiiiaiiiitiMiMM^^ darker

Blue or Dark Green

Dark Red or Blue

Red or Dark Blue

Red or Dark Yellow
Neutral Density Filters

The neutral density filter and the polarizing filter are two types of filter which have an important

property in common. They both affect all colors

approximately the same, and therefore have no pronounced color. Neutral density filters are used to reduce the intensity of all wavelengths

of light by equal amounts. They are marked in terms of optical density units. An 0.3 neutral

density (ND) filter transmits 50 percent of the

light reaching it; a 1.0 ND filter transmits 10

percent of the incident light; and a 2.0 ND filter transmits 1 percent. The densities of two filters used together must be added in order to get the

overall density of the combination. Thus, two

0.3 filters have an ND of 0.6 and transmit 25

percent of the incident light. ND filters are of value for use with the faster lenses which can

only be stopped down to f/11 or f/16. When a

fast lens must be used with a fast film in bright

light and the camera shutter speed cannot

prevent overexposure, adding an 0.3 ND filter reduces the light by one stop, 0.6 ND by two

stops, 0.9 ND by three stops and so on.

Neutral density filters are of two types: solid glass, in which light is absorbed in the glass,

and evaporated metal film, in which most of the

light that is not transmitted is reflected. Two

evaporated metal film neutral density filters should not be used together, because the

densities do not add linearly. Multiple reflections

between the filters will cause the density of the

combination to be less than the sum of the two

densities, and can produce undesirable

interference effects.

Polarizing Filters

The polarizing filter is quite different in its effect than the ND filter. It, too, absorbs all colors of

light equally. But light has another property,

which is not directly visible to the eye:

polarization. Light is partially polarized

whenever it is reflected from a shiny surface

such as window glass. A normal photograph of a window may show only the reflection, and

nothing behind the glass. Place a polarizing

filter over the camera lens and rotate it. In most

instances, one position of the filter can be found

where the glass reflection will be greatly

reduced or eliminated entirely, depending on how strongly polarized the light is. The use of large polarizing filters placed over light sources

in conjunction with a filter at the lens gives

almost complete control of reflections. A

polarizing filter always requires at least a one

stop exposure increase, since it cuts out at least half the light it receives.

Haze Filters

The haze filter is especially valuable in law en- forcement work. It is a clear glass filter which

has no effect except to hold back the ultraviolet wavelengths. In all except extreme distance

views, the effect of the filter on the picture is nil.

It does serve as an excellent mechanical

protector and "transparent lens cap" for the

lens. Dust, dirt, scratches, and fingermarks get on the inexpensive, easily replaced haze filter, instead of the front lens element. Haze filters are available, anti-reflection coated, to prevent

ghosts when used facing strong light sources.

Tripods

No law enforcement photographer can work

without a tripod or some other form of camera

support. The tripod is the traditional, most

readily available, and probably most convenient

support. A tripod should be tall enough to hold

the camera comfortably at eye level, and should

fold small enough that it is not too cumbersome

in the camera kit or squad car. An adjustable

"elevator" post in the center will save a tremendous amount of time setting up for the

required perspective. A quick-release plate for the camera is a great convenience when the camera is attached and removed frequently.

Tripods that vibrate excessively are of little value. Many do so, but can easily be identified. Put a camera with a very long focal length lens on the tripod. Outside at night, point the lens at a street light a few blocks away. Take a picture

of the light at each shutter speed on the camera, plus some time exposures, say 3, 5 and 20

seconds. Try not to overexpose, and use

neutral density filters if necessary for the long

exposures. Focused sharply, the street light

should be no more than a speck, like a star, on

the negative. Examine the street light image
critically with a 10 power magnifier. If the tripod

is vibrating on any of the exposures, a characteristic pattern will show as the innage of the light moves on the film. This will be different than the

increased image size caused by overexposure.

Many times it is a figure-eight type pattern, but

any sign of a snake-like path indicates

excessive vibration at that shutter speed.

Thereafter, use much higher or lower speeds.

The good tripod will be firm enough for the

longest focus lens normally used, easy to adjust, not too heavy, and will not pinch fingers.

Make sure the tripod is adaptable to both hori- zontal and vertical positions with all cameras

and lenses.

A pan tilt head is a very necessary accessory

for use with a tripod. It permits the camera to be

pointed in any direction and then locked in position.

Copy Stands

This is one of the most useful accessories for the smaller department which cannot justify a

separate copy camera. A popular type is built very much like a 10 x 12.5 cm (4 x 5 in) vertical enlarger with no lamphouse. External lights are provided to evenly illuminate the full baseboard of the stand. The "enlarger" part is really a 10 x 12.5 cm (4 x 5 in) camera with a

long bellows, ground glass, and a reflex focusing hood so the operator can look horizontally into the ground glass, instead of having to climb a ladder or put the stand on the floor. Similar units are available to which a press,

single lens reflex or other type of camera can

be attached. Adapter backs will make sheet

film, roll film, 35 mm color film, and instant

process film available for use on the copier. For

reproducing identification photos, fingerprint

cards or documents of any kind with a wide

range of sizes, or for any type of small object

(macro) photography, the copy stand is both

convenient and time saving compared to improvised set-ups. Process type lenses are

available for the complete assembly. These are corrected for giving images up to 20 times

actual size.

Miscellaneous

The list of other accessories is endless. Special

mention is made of slave units which can be

attached to individual electronic or photoflash

lamp units. When areas must be photographed

with supplementary light, any number of flash

units can be located at strategic points. When

the main flash at the camera is fired, all the

slave units fire too, without any wire

connections to the camera. With electronic

flash at each unit, the firing is simultaneous with

the main flash. With photoflash lamp units, the

slaves will all fire together, but ail will be

delayed from the main flash by about 20

milliseconds and the shutter speed must be

lengthened accordingly.

Focusing magnifiers and angle viewers have

occasional value. They are available for many

cameras. Many times, a long cable release or a

remote camera tripping device will be essential.

A cable release should always be used with a camera on a tripod to prevent hand vibration. If you do not use haze filters on all your lenses,

the use of a lens brush or ear syringe "blower"

to remove dust before attempting to clean a

lens will protect the lens against scratches.
Hi,

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. D C 20234

OFFICIAL BUSINESS

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