Photography as an Aid to Scientific Work

PHOTOGRAPHY AS AN AID TO SCIE TIFIC WORK

PHOTOGRAPHYas an aid to

SCIENTIFIC WORK

An I L FOR 0 Textbook

Published by

ILFORD LIMITED ILFORD LONDON1950

Contents

SECTION ONE Pages 1 to 3General considerations in selecting photographicmaterial and technique for a particular task

SECTION TWO Pages 4 to 14Analysis of Ilford materials according to their

characteristics

SECTION THREE Pages 15 to 42Materials recommended for specific purposes

SECTION FOUR Pages 43 to 46Determining exposure time

SECTION FIVE Pages 47 to 50Safelights

SECTION SIX Pages 51 to 60Processing

SECTION SEVEN Pages 61 to 64Filters and wedges

SECTION EIGHT Page 65Photographic apparatus

SECTION NINE Pages 66 to 68Ilford publications

v

Note to the Eighth Edition

Another edition having been found necessary, theopportunity has been taken to rewrite the bookcompletely. The recommendations for specificpurposes are more precise than formerly and thesection containing these has been arranged inalphabetical order of applications. It is hoped thatthis, together with the contents list on page v,will make the book largely self-indexing.

Considerable progress in manufacture has takenplace since the last edition of the book appearedand a large number of plates and films are includedfor the first time. The availability of materials is,of course, subject to change.

ja/lllaty, 1950

VI

Preface

The importance of photography to science and industry is rarely fullyappreciated, yet without the aid of photography a very great number ofmodern industrial processes and methods of research would be impossible.In addition, photography plays a routine part in almost every laboratoryfor illustrating reports and lectures, duplicating graphs, etc.

The selection of the most suitable materials and technique for any parti-cular work frequently constitutes a problem in which the manufacturerof photographic materials is specially well placed to help. For manyyears Ilford Limited has played a leading part in rendering photographicservice to scientists in the universities and other research centres, and inindustry, both at home and overseas. Science and photography aremutually indebted-each assists the rapid advance of the other-andIlford Limited has benefited greatly from co-operation with scientificworkers and has, for its part, been able to provide valuable assistance insolving the problems of the latter.

Among the fields to which Ilford Limited has made outstanding con-tributions are :-

Cathode ray oscillographyElectron micrographyIndustrial radiographyMedical radiographyNuclear physicsPhotomicrographySpectrography

Special Ilford products for these purposes are backed by an unsurpassedrange of plates, films and papers for general work.

The object of this book is to describe the characteristics of each of themany Ilford products, and to indicate, where possible, the materials mostsuitable for any particular purpose.

It is not practicable in a book of this nature to make recommendationsthat will meet the needs of every scientist, but Ilford Limited welcomesenquiries about specific problems. Enquiries of this nature may concernthe use of standard Ilford photographic materials, problems calling forspecial materials or processes, or new or unusual applications ofphotography to scientific work.

ILFORD LIMITED

Vl1

ELECTROMAGNETIC EXPANDED VIEWSPECTRUM OF VISIBLE REGION

WAVELENGTH (3900-7600A)em. WAVELENGTH

-1510 0'0001 XU .- 36

-14 ULTP,A-VIOLET10 0'001 XU I- 38

-13I- 4000 A10 0'01 XU 400 m~

-12 VIOLET10 O·IXU I- 42-II

10 IXU 44

GAMMA RAYS-10

10 10XU BLUE I- 46-9

THERAPEUTIC X 10 100XU I- 48DIAGNOSTIC :!o -8

>- 10 IA BLUE-GREEN I- 5000 A 500 m~GRENZ RAYS -< -7V>

10 ! mp I- 52-6 G'REEN

Ul TRA-VIOLET I- 10 10m~ I- 54-5

I- 10 100m~ YELLOW-GREEN I- 56VISIBLE LIGHT -.

PHOTOGRAPHIC 10 I~ YELLOW I- 58zHEAT "T1 -3

;;0 I- 10 10~ I- 6000 A 600 m~RADIATION 1>

-2 ORANGE;;0I- 10 100~ I- 62m

0 -II- 10 Imm I- 64

1-1 lemRED

I- 66

I- 10 10em I- 682

HERTZIAN I- 10 1m 7000 A 700 m~

(WIRELESS)3

I- 10 10m 1-72WAVES • DEEP RED

I- 10 100m I- 745

10 I krn 766

10 10km INFRA-RED I- 78

SOOOA 800 m~EQUIVALENTS

-4I~ = I micron = 1/1000mm = Ix 10 em

-7I m~ = I millimicron = 1/1000)J = Ix 10 em

-8IA = I angstrom unit = 1/10m)J = Ix 10 em

-III XU = I X-unit = 1/1000A = I x 10 em

viii

SECTION ONE

General considerations zn selectingphotographic material and techniquefor a particular taskIt is recommended that photographic material be selected usually byreference to the following considerations, taken in the order given:

(0) nature of radiation to be recorded,(b) sensitivity and contrast required,(c) duration of exposure,(d) special grain requirements, if any,(e) need for special techniques at the exposing or processing

stages,(f) physical form of the material, e.g., plate, film or paper, cut

sheets or rolls.

NATURE OF RADIATION TO BE RECORDEDThis factor is fully considered in Section Two in which all the Ilford Plates,Films and Papers likely to be of use in scientific work, some of whichhave been specially produced for particular scientific problems, areclassified according to their spectral sensitivity. To avoid the need forunduly dim safelights, materials sensitive to the longer-wave regions of thevisible spectrum should not be chosen unless sensitivity is needed insuch regions: in an obvious example, if the problem involves therecording of U.V. spectra, panchromatic emulsions should be avoidedas they offer no advantage in sensitivity over non-colour-sensitizedmaterials.

SENSITIVITY AND CONTRASTHaving selected the material according to the radiation to be recorded,the relative sensitivity level (speed) and contrast should next be coo-sidered. If only a "two-tone" record is desired, as when copying aline diagram, the highest contrast consistent with adequate sensitivityshould be chosen. Materials of lower contrast are needed for continuous-tone records, or for records which may contain a range of intensities, asin spectrography, or of exposure times, as in some oscillograph recording.As a general guide, it should be remembered that higher sensitivity isusually associated with lower contrast, though exceptions will be found.It is not possible to combine maximum speed with maximum contrast,or with extremely low graininess.

2 PHOTOGRAPHY AS AN AID TO SCIENTlFIC WORK

DURATION OF EXPOSUREAll emulsions exhibit to some extent the phenomenon known as " re-ciprocity failure." The photographic effect falls off all extremes ofillumination, both high and low, but the degree of this falling off andthe region at which maximum photographic effect is obtained variesfrom material to material. This phenomenon is frequently referred to as" I.t failure" since it relates to the failure of the emulsion to give thesame photographic effect when I (illumination) and t (time) are variedproportionately.

Modern materials most suitable for snapshot exposures of the order ofIf25th sec., are not so fast when exposure times are of seconds' orminutes' duration. Some of the older types of materials are preferablefor such work and are therefore retained in the Ilford range.

In a great deal of ordinary photography there is no need to pay muchattention to this factor, but in work where maximum speed is desirablewith exposures of unusually long or short duration reciprocity failuremust be taken into account.'

The Ilford Plates most suitable for long and short exposures respectivelyare as follows :-

Most suitable exposure durationIlford PlatePanchromatic

Astra VIIIAstra IIIHP3

OrthochromaticSelochromePress Ortho Series 2

Non-colour-sensitiveZenith Super-sensitive LongZenith Astronomical LongBlue-sensitive, Type LN ShortReciprocity failure may on occasions be put to good ,use. For example,

a user of the Press Ortho Series 2 plate (a plate most efficient at shortexposures) reports. . .. "The great advantage of these plates is thatthey are relatively insensitive to the faint background of the night sky,yet very rapid to the relatively bright, almost instantaneous, flash of themeteor, enabling an exposure of up to two hours at] /2.5 to be givenwithout much sky-fogging of the plate."

SPECIAL GRAIN REQUIREMENTSThe grain of photographic materials influences both the appearance andthe resolution of detail of photographs taken with them. Unless thephotographic record is to be enlarged 10 diameters or more, the graininessof the developed image can usually be ignored. Graininess is occasionallya dominant factor, however, as in graticule work. Adequate finenessof grain can then be secured only, as a rule, at the cost of reducedsensitivity.

LongLongShort

ShortShort

I

SELECTING PHOTOGRAP HIC MATERIAL AND TES::HNIQUE 3

SPECIAL TECHNIQUES

Generally the sensitive material is exposed without special pre-treatmentand is processed, after exposure, in conventional processing baths.Sometimes, however, pre-treatment of the material may be desirable orthere may be need for special processing conditions. Such variationsfrom ordinary practice, which are dealt with more fully later, include :-

(0) prior treatment of the emulsion surface with a fluorescentmaterial-required when ordinary materials are used to recordshort-wave ultra-violet radiation (page 60),

(b) prior hypersensitization of the material by exposure to mercuryvapour or by bathing methods; or techniques of supplementarypre- or post-exposure, with the same object in view (page 58),

(c) prior bathing of the material in a solution of a desensitizingdye (page 55),

(d) special rapid processing techniques-useful in some cases ofoscillograph recording (page 57).

PHYSICAL FORM OF THE SENSITIVE MATERIAL

The materials in general use as supports for photographic emulsionsare as follows :-

Glass plateEmulsions coated on glass plate are widely used for scientific work.The greatest advantages of this form of base are rigidity and dimensionalstability.

FilmIndividual flat sheets or rolls. Film base is usually cellulose acetate(safety) or cellulose nitrate. With flat films there is sometimes a choiceof thickness.

Plate and film are both in general use for negatives.

PaperIn general use for positives (prints), but also for certain negative materials.The least costly of the three types of base.

Special emulsions required in small quantities are invariably coated onglass plate. Manufacturing problems prohibit the coating of smallquantities on film and paper.

-=

SECTION TWO

Analysis of Ilford materials

according to their characteristics

The sensitive materials of the Ilford range are here grouped under thethree main types of support, viz., plates, films and papers, with anadditional grouping for X-ray films and paper. Colour films have beenexcluded from this Section. ,

PLA TES AND FILMS

I

Plates intended for recording other than visible or near-visible radiationhave been grouped on their own. Other plates and films have beengrouped according to their spectral sensitivity. Not all the materials inone spectral grouping have exactly the same spectral range of sensitivity,but the range applicable to each material is specified.

Sensitivity ranges are specified by wavelengths in angstrom units. Therelation of these wavelengths to the colours of the spectrum is shownin the diagram at the front of the book.

In general, within each spectral grouping, materials are placed in orderwith the lowest speed and the highest contrast at the top, and the highestspeed and the lowest contrast at the bottom. Speed, contrast and grainof each material are described in general terms.

A more precise indication of the speed of those materials which areemployed for general photography can be obtained from the table ofrecommended meter settings given at the end of this Section.

PAPERS

Papers differ widely in characteristics and cannot be ,classified in quitethe same way as.plates and films. In general, however, they have beenarranged with the slowest at the top, relative exposures to tungsten lightproviding an indication of relative speed. The colour sensitivity ofeach paper is stated.

X-RAY FILMS AND PAPER

In this table, materials have been arranged with the slowest at the top,speed and contrast being described in general terms. Separate descrip-tion's are given for screen and non-screen use.

ANALYSIS OF ILFORD :MATERIALS 5

TABLE 1 ILFORD PLA TES

For recording other than visible or near-visible radiation

Name Nature of radiation to be recorded

*Q Q Plates are specially made for recordingradiation of low penetrating power. They areof particular value in :-

(a) the recording of positive ions, as inmass spectrography,

(b) the recording of all electromagneticradiation over the band from very softX-rays of a few A.D. to ultra-violetup to about 2,000 A.D.

Because of the fragile nature of their emulsionQ Plates should not be used where otherstandard plates will work equally Voiell.Q Plates are made in three speeds-Ql Slow,Q2 Medium, Q3 Fast. Grain size and contrastof these plates are in the order of their speeds,Ql being the finest grained and most contrasty.Of the three plates, Ql is generally to bepreferred, having the finest grain.Q3 Plate should not be used unless Q2 isdefinitely not sensitive enough.Q Plates are non-colour-sensitive.

*Photomechanical T847 A non-colour-sensitive plate of extremelyhigh contrast for use in electron micrography.

*Rapid Process(Experimental)

A non-colour-sensitive plate of high contrastfor use in electron micrography for whichwork it has very high speed.

uclear Research Emulsions-Type C2 Records protons to SOMeV and gives good

discrimination between particles of lowenergy.

Type B2 Slightly more sensitive and of coarser grainthan C2.Both the above materials are well suited forapplication in geological survey of radio-active minerals.

I ,"Jllf 1110l"Y produc: made to order oniy, Continued on next page

-

6 PHOTOGRAPHY AS AN AID TO SCIENTIFIC WORK 7ANALYSIS OF ILFORD MATERIALS

Nature of radiation to be recordedName Spectralrange of

sensitivitySpeed Contrast GrainName

*Nuclear Research Emulsions (Continued)Of slightly finer grain and less sensitivity thanC2, so that protons give heavy tracks only atthe end of their- range. Good tracks froma-particles of fairly low energy.Of still lower sensitivity so that only verystrongly ionizing particles such as fissionfragments give heavy tracks.A new, very sensitive emulsion for recordingparticles of very low ionizing power, includingelectrons. Particles at greater ionizationproduce heavy tracks readily observed by dryobjectives so permitting rapid plate scanning.In thin layers suitable for autoradiography.Nuclear Research Emulsions are non-colour-sensitive.

Type El, Special Lantern, 2300-S200A SlowNormal

Medium to Very finehigh

Type Dl Medium to Finehigh

Special Lantern, 2300-S200A SlowSoft

Type GSOrdinary 2300-S200A Slow Medium to Fine

high

Special Rapid 2300-S200A Slow Medium Fine

*Rapid Process 2300-S200A Medium(Experimental)

High Fine

2300-S200A Medium Medium Mediumenith Super-sensitive

TABLE 2 ILFORD PLATES

Sensitive to blue and shorter wavelengths*ZenithAstronomical

2300-S200A Medium Medium MediumSpectral

Name rangeof Speed Contrastsensitivity

Grain2300-S200A Fast Medium Medium*Blue-sensitive

Type LNExtremely

fineContact Lantern 2300-4000A Very slow Extremely

high

TABLE 3 ILFORD PLATESVery slow Extremelyhigh

Extremelyfine

2300-4000Aand4400-S300A

*HighResolution Sensitive to green and shorter wavelengths

Spectralrangeof

sensitivityExtremely

fineVery slow Extremely

high*Photomechanical 2300-4900AT847

Name Speed Contrast, Grain

Very fineSlow Very high2300-S300AThin FilmHalf Tone

I.it ho-neg 2300-S800A Slow Extreme! y Very finehigh

Very fineSlow High2300-S200AProcess Orrho ITalfTone 2300-S800A Slow Very high Very fine

Very fineSlow HighSpecial Lantern, 2300-S200AContrasty

(Iu'umatic 2300-S800A Slow Medium to Finehigh

+Laboratory producr made 10 order only, /"lil(JI'''/I)f''V produc: "lade to order onlY. Continued on next page

8 PHOTOGRAPHY AS AN AID TO SCIENTIFIC WORK

Name GrainSpectralrange of

sensitivitySpeed Contrast

*Astra VI 2300-5700A Medium Medium Medium

Selochrome Medium2300-5800A Fast Medium

Press OrthoSeries 2

2300-5800A Very fast Medium Medium

TABLE 4 ILFORD PLA, TES

Sensitive to red and shorter wavelengths

Name GrainSpectre!range of

sensitivitySpeed Contrast

Thin FilmHalf TonePanchromatic

2300-6600A Slow . Very high Very fine

*Astra I Fine2300-6200A Slow High

Rapid ProcessPanchromatic

Fine2300-6700A Medium High

*Astra VII 2300-6700A Medium High Fine

FP Special 2300-6700A Medium Medium to Finehigh

Special RapidPanchromatic

2300-6500A Medium Medium Fine

Medium*Astra VIII 2300-7100A Fast Medium

Soft GradationPanchromatic

Medium2300-6500A Fast Medium

*Astra III 2300-7000A Fast Medium Medium

HP3 Medium2300-6700A Extremely Mediumfast

*Laboratory product made to order onfy.

ANALYSIS OF ILFORD MATERIALS 9

TABLE 5 ILFORD PLATES

Sensitive to infra-red and shorter wavelengths

NameSpectralrange of

sensitivityGrainSpeed Contrast

Infra-redProcess

2300-5200Aand

7400-8800A

Slow High Very fine

*Long-range-spectrum

2300-8800A Medium High Fine

TABLE 6 ILFORD FILMSSensitive to blue and shorter wavelengths

NameSpectralrange of

sensitivityContrast Grain

Types of. film

availableSpeed

SlowContact

2300-4900A Flat Very slow Extremely Extremelyhigh . fine

ontact 2300-4900A Very slow Extremely Extremelyhigh fine

Flat

Line 2300-5300A Flat Slow Very high Very fine

Recording 2300-5300AKHOt

Flat Slow Vcry high Very fine

I{t'cording 2300-5200A1111

Rolls(standardrecordingfilm widths)

Slow High Very fine

Ilillt' Grain~illI'l yI',,·Ii Ii V"

2300-5200A 35 mm. and Slow16 mm. formicro-copying

16 mm. cinepositive

High Very fine

I'lpr(' 2300-5200A Flat Slow High Very fine

'II/Jlm/lor'Y pror/lfct made to order onfy. Continued on next page

10 PHOTOGRAPHY AS AN AID TO SCIENTIFIC WORK ANALYSIS OF ILFORD MATERIALS 11

Spectral Types oj TABLE 8 ILFORD FILMSName range oj film Speed Contrast Grain ~ Sensitive to red and shorter wavelengthssensitivity arailable

Recording 2300-5200A Flat Slow High Very fine Spectral Types oj8B21 Name range oj film Speed Contrast Grain

sensitivity availableFine Grain 2300-5200A Flat Slow Medium Fine Panchro- 2300-6700A Flat Slow Very high ExtremelyOrdinary line fine

Recording 2300-5200A Rolls Medium MediumFast5B52 (standard Pan F 2300-6700A 16 mm. cine Medium Medium to Very fine

recording negative high. film widths) 35mm .

miniature35 mm. and

TABLE '7 ILFORD FILMS 16 mm. forSensitive to green and shorter wavelengths micro-

copyingSpectral Types oj FP3 2300-6700A Flat Medium Medium FineName range oj film Speed Contrast Grain

sensitivity ami/able Roll35mm.

Litho-neg 2300-5900A Flat Slow Extremely Very fine miniature

high Hyperpan 2300-6700A Roll Fast High MediumI' Aerial

Rapid 2300-5900A Flat Slow Very high Very fineOrtho-line IIPX 2300-6700A 35 mm. Very fast Medium Medium

andMicro-neg 2300-5900A 35 mrn. and Slow Very high Very fine 70 mm. rollsOrtho 16 mm. for

micro-copying R 'cording 2300-6700A Rolls Very fast Medium Medium5RJOl (standard

Commercial 2300-5900A Flat Medium Medium Medium recordingOrtho film widths)

Selochrome 2300-5900A Flat Fast Medium Medium HI I ording 2300-6700A Flat Very fast Medium MediumRoll HH I()I

Recording 2300-5900A Rolls Very fast High Medium III' , 2300-6700A Flat Very fast Medium Medium5G91 (standard Roll

. recording 35mm .film widths) miniature

16 mm. cineHyper- 2300-5900A Flat Extremely Low Coarse 'negativechromatic fast Aerial

)

-

'12 PHOTOGRAPHY AS AN AID TO SCIENTIFIC WORK 13ANALYSIS OF ILFORD MATERIALS

TABLE 9 ILFORD PAPERS TABLE 10 ILFORD X-RAY FILMS AND PAPER

Coloursensitivity

Relative exposureto tungsten light

I

Name Speed ContrastName

Autopos Sensitive tolight of allcolours

Very slow, forexposure to intenselight sources

For use without fluorescent intensifying screens

Contrast Dental X-ray Film Very highSlowNon-colour-sensitive

Reflex Contact Document Nos.50 and 50 Matt

1500

Very highIndustrial X-ray Film C Slow tomediumContact Document No. 9S on-colour-

sensitive1500

Medium to highMediumX-ray PaperContact (Normal grade) on-colour-

sensitive700

MediumMedium tofast

Standard X-ray FilmBromide, Special for Carbro Non-colour-

sensitive16

HighFastIlfex X-ray FilmSlightlyorthochromatic

16

HighFastIndustrial X-ray Film BMultigrade (with M.6 filter) Slightly

orthochromatic12

tandard Dental X-ray Film HighFast

Document Nos. 7 and 9 Non-colour-sensitive

8MediumVery fastRed Seal Xvray Film

Bromide (Normal grade) Non-colour-sensitive

7 MediumVery fastIndustrial X-ray Film A

lIor use with fluorescent intensifying screensPhotomechanical Non-colour-sensitive

6

Medium to highFast1". Y Paperon-colour-

sensitiveDocument No. 60 5

Hight.uulard X-ray Film Fa t

Ortho Photomechanical Orthochromatic 2Highi.uulnrd Dental X-ray Film o. 3a FastOrthochromaticOrtho Stripping 2

Document Nos. 1, 4 and 4T Orthochromatic Medium1 Extremelyfast

HI d Seal X-ray Film

Recording GPS Orthochromatic 1

MediumExtremelyfast

111.111 111.d X ray Film ARecording BP1 Non-colour-sensitive

1/8


RECOMMENDED EXPOSUREMETER SETTINGS FOR ILFORD PLATES

AND FILMS

*B.S.I. tA.S.A.,

Daylight I Tungsten Daylight IMaterial Tungsten

PlatesSpecial Rapid Panchromatic 24° 22° 20 12FP Special 26° 25° 32 25Soft Gradation Panchromatic 27° 25° 40 25HP3 33° 32° 160 125Chromatic 17° 14° 4 2Selochrome . 29° 26° 64 32Press Ortho Series 2 30° 27° 80 40Ordinary 15° 9° 2.5 0.6Soft Ordinary 15° 9° 2.5 0.6Special Rapid 20° 14° 8 2Zenith Super-sensitive 24° 18° 20 5

Flat, Roll and35 mrn. Miniature FilmsPan F (MF) 24° 22° 20 12FP3 (FF, RF, MF) 26° 25° 32 25HP3 (FF, RF, MF) 31° 30° 100 80Commercial Ortho (FF) 26° 23° 32 16Selochrome (FF, RF) 29° 26° 64 32Hyperchromatic 33° 30° 160 80

FF=Flat film. RF=Roll film. MF=35 mm. Miniature film.

16 mm. Cine Negative FilmsPan FHP3

20100

1280

* British Standards Institution. These settings are intended for meterscalibrated in B.S.r. degrees but are generally also suitable for usewith meters scaled in Scheiner and similar logarithmic ratings.

t American Standards Association. These settings are intended formeters calibrated in A.S.A. Numbers but are generally also suitablefor use with meters scaled in Weston, G.E. and similar arithmeticratings.

SECTION THREE

Materials recommended for

specific purposes

In the following pages a large number of scientific applications ofphotography are listed in alphabetical order. A brief description ofeach application is given with a list of the Ilford materials recommendedfor the work .

More than one material may be suitable for a particular branch of work.Sometimes the factors governing the choice of each material are stated:sometimes a number of alternative materials are given without qualifi-cation. In the latter case, consideration of the characteristics of eachmaterial, given in the tables in Section Two, will facilitate the selectionof the material best suited to the work in hand.

The materials named in the following pages are those likely to be mostsuitable for the great majority of work, but the possibility that a materialnot included among those recommended may be the best under certaincircumstances must not be excluded. Again, a careful study of theinformation given in Section Two coupled with a right appreciation ofthe nature of the work will be the best guide in the selection of thematerial.

AERIAL PHOTOGRAPHY

In luding reconnaissance and photogrammetry.

Materials recommendedl/ford Hyperpan Aerial Film. For air photography in daylight: recorn-

nu-ucled for all normal work. The emulsion is specially hardened inmnnufacture and may be processed at high temperatures without the11(,(,d f r special precautions to avoid softening during development.

lifOI'd IIP3 Aerial Film. A film of somewhat higher speed but lowerI unt rnst than Hyperpan Aerial Film. Suitable for low-altitude workvlu-r« subject contrast is high.

Illlml I TP3 Plate. For use when plates are required.


ASTRONOMY

Including astronomical spectrography.

Materials recommended

FACTORY-COATED PLATES

The following plates make up a useful range :-Ilford HP3 Plate. A plate of extremely high speed when exposure

times are short, as in the photography of rapidly moving objects, suchas meteors. The red sensitivity is high, extending to 6700A, with apeak at 6500A.

Ilford Rapid Process Panchromatic Plate. Medium speed, high contrastplate, suitable for exposure times of minutes' duration. Similar coloursensitivity to HP3 Plate.

Iljord Thin Film Halj Tone Panchromatic Plate. Slow, highest contrast,fine grain panchromatic with broad peaks at 5200A and 6400A.

Iljord Press Ortho Series 2 Plate. Comparable with I-IP3 Plate in speed,but sensitized to 5800A with a peak at 5600A.

Iljord Chromatic Plate. Medium speed, high contrast, colour sensitivitysimilar to Press Ortho Series 2 Plate.

Iljord Special Rapid Plate. Medium speed, medium to high contrast,slower and finer grain than Zenith Astronomical Plate (see below).

LABORATORY PRODUCTS

The following plates can be coated to special order:-Ilford Zenith Astronomical Plate. High speed, medium contrast plate,

non-colour-sensitized. For use when exposure times are long.

Liford Astra I Plate. Slow, high contrast, fine grain plate, stronglysensitized between 5200A and 6000A.

Iljord Astra III Plate. A fast, panchromatic plate of medium grainand contrast. The" green gap" has been much reduced, givingsubstantially even sensitivity to tungsten light (2850° K) from 4000Ato 7000A.

Liford Astra VI Plate. A medium speed plate with maximum sensitivityat 5300A, used for work on the solar corona. Formerly known as theC Plate

Ilford Astra VII Plate. A special version of the Rapid Process Panchro-matic Plate sensitized to give a peak at 6450A with little sensitivitybeyond 6560A. Formerly known as Hydrogen Alpha Plate Type 1.

Iljord Astra VUI Plate. Similar in speed, grain and contrast to Astra III,but sensitized very evenly around the hydrogen alpha line and tobeyond 6800A.

MATERIALS RECOMMENDED FOR SPECIFIC PURPOSES 17

ATOMIC DISINTEGRATION

See NUCLEAR RESEARCH

AUTORADIOGRAPHY

A method of locating radioactive elements by covering specimenswith a photographic emulsion. The specimens are often histologicalsections in which radioactive substances emitting ~-rays are incorporatedas tracers, and a photographic emulsion is mounted in close contactwith the section. In some cases the emulsion is stripped from the glassfor this purpose, and in others may be melted and run on to the specimen.Histological specimens are sometimes "floated on" the emulsion, thespecimen and emulsion being afterwards dried.

The method has also been used to ascertain the distribution of radio-active elements in minerals.

Materials recommendedIljord Special Rapid Plate.Iljord Process PlateIljord Thin Film HaljTone Plate

I speed~ decreasing

As this technique is comparatively new and is still being developedthese recommendations must be regarded only as general.

The choice of plate will often depend on the degree of resolution andthe subsequent enlargement required. The plates listed above are inorder of increasing resolving power and decreasing speed. Processand Th.in Film Half Tone Plates are available as stripping plates.

Liford Nuclear Research Emulsion, Type G5. In thin layers this emulsionnlso is suitable for autoradiography.

ReferencesI.. I:. Belanger and C. P. Leblond, Endocrinology, 39, 8-13, July, 1946. S. R. Pclc,Nut urc, 160, 749-750, 29th November, 1947. C. P. Leblond, W. L. Percival and1 (,ross, Proc.Soc.Exp.Biol.Med.,67, 74-76, 1948. T. C. Evans, Proc.Soc.Exp./llol.l\lcd., 64, 313-315, 1947.

CARDIOGRAPHY

\f~ I~LECTRO-CARDIOGRAPHY (E.C.G.) A D ELECTRO-IiNCI ,:PIIALOGRAPHY (E.E.c.)

CATHODE RAY OSCILLOGRAPHY

II\( cathode ray tube is one of the most versatile electron tubes whichIt y 1 been devised. Already it has innumerable applications and, as

t 1''' ihilirics become more widely known, its use will extend. For


many purposes visual observation of the trace is sufficient, but sooneror later a desire for a record of the trace arises. Photography providesa ready means of obtaining such a record. There are two main methodsof obtaining records, the difference between them being the mode offormation of the latent image. This may be effected :-

(a) by the direct action of the electrons: for this the materialmay be either inside or outside the tube, depending on theequipment used.

(b) by the indirect action of electrons, i.e., fluorescent screenphotography: this can be achieved either by pressing thematerial in contact with the screen or by using optical meansto form an image of the trace on the material. The lattermethod is the more usual one.

For a full discussion of the problems involved in this work see" ThePhotographic Recording of Cathode Ray Tube Traces" by R. J. Hercock,Ilford Limited, 1947. This contains an extensive bibliography on thesubject.

Materials recommendedFor recording work a wide range of Ilford Plates, Films and Papers

can be used, but Ilford Recording Films and Papers have been speciallydeveloped for oscillography, and their use is, therefore, recommended:they are described under RECORDI G.For recording fry the direct action of high-voltage electrons:

Ilford Recording Film 5BllIlford Recording Film 8B21Ilford Selochrome Roll FilmIlford Process Plate.

For recording fry the direct action of low-voltage electrons:Ilford Q Plates (see page 5).

For recording blue screens:Ilford Recording Film 5B52Ilford Recording Film SG91Ilford Recording Film 5R101Ilford Recording Paper BP1Ilford HP3 Plate.

For recording green and)lellow-green screens:Ilford Recording Film SG91Ilford Recording Film SR101Ilford HP3 Plate.

For recording red screens:Ilford Recording Film SR101Ilford HP3 Plate.The relative speeds of the materials recommended for fluorescent screen

photography are given on the next page :-

I

i

II

MATERIALS RECOMMENDED FOR SPECIFIC P.URPOSES 19

Colour of screen fluorescenceMaterial

Blue Green Yellow- Green

Recording Film SR101 4 2 3HP3 Plate 4 2 3Recording Film 5G91 4 2 2Recording Film 5B52 1Recording Paper BP1 2

ReferenceR. ]. Hercock, R. G. Hopkinson, W. F. Berg, W. Nethercot, "The PhotographicRecording of Cathode Ray Tube Screen Traces," Photo ]., 86B, 138-164, Nov.-Dec., 1946.

CINEMATOGRAPHYSee also CINE-RADIOGRAPHYA complete range of Ilford 16 mm. film stock is av:ailable. The negative-positive system is employed, i.e., the film exposed in the camera isprocessed to form a negative from which are printed the positive copiesto be used for projection. This contrasts with the reversal system inwhich the film exposed in the camera is processed to give a direct positive.

For industrial cinematography the negative-positive system has manyadvantages :- .

(i) Any number of first-class copies can be made.(ii) If the positive copy is scratched or destroyed, further perfect

copies can be made from the negative, which does not passthrough the projector and is therefore in its original condition.

(iii) Editing can be carried out on the negative, and positivesfrom this will be free from joins, facilitating high qualityprojection.

(iv) The system has great latitude in exposure. Ilford negativefilms have great inherent latitude and, in addition, compen-sation can be made for exposure errors by controllingdevelopment. Yet further correction is possible by controlof exposure when printing the positive.

Materials recommendedIlfordPanF 161JJ1JJ.Cine Negative Film. For general outdoor photography.'(lord HP3 16 1JJm.Cine Negative Film. For difficult lighting conditions,indoors and outdoors.Ilf()rd 16 mm. Fine Grain Safety Positive Film. For the preparation of positivet opics from 16 mm. cine negatives. May also be used in the camera forI,hot graphing title cards, typescript or diagrams, and other animation\(11·1.

II llford 16 mm. Cine Films are on safety base.

-

!

I20 PHOTOGRAPHY AS AN AID TO SCIENTIFIC WORK

CINE-RADIOGRAPHY

INDIRECT METHODCinematography of the image produced on a fluorescent screen byX-rays passing through the object under investigation.

Materials recommendedllford HP X Film. For maximum speed.llford Recording Film 5G91. For maximum contrast.

References

Industrial. S. L. Fry, " Cine Radiography-Application to the investigation of metalpouring," Metal Industry, 67, 2-6, 6th July, 1945, and 25-28, 13th July, 1945.Medical. Russell J. Reynolds, C.B.E., M.B., D.M.R.E., British Journal of Radiology,7,415-424, July, 1934.

DIRECT METHOD•Using film in rolls, in width to give 5 in. X 5 in. frames. These are then

copied by reduction frame by frame on to 16 mm. or 35 mm. cine film.

Materials recommendedFor original radiographsIlford Standard X-ray Film.For 16 mm. or 35 mm. copiesIlford Recording Film 5G91.

ReferenceMedica/. A. E. Barclay, X-ray Cinematography in Research, •British Journal ofRadiology, 13,227-234, July, 1940.

CLINICAL PHOTOGRAPHYSee MEDICAL PHOTOGRAPHY.

COLOUR PHOTOGRAPHY

Many processes are in general use for the reproduction of objects incolour. In some, all the stages of the process are photographic: inothers as, for example, in printing from colour blocks, only some of thestages are photographic. Colour correction of printing plates involvesmuch skilled hand-work.

Ilford materials are available for much of this work, including thepreparation of the following :-

Colour transparencies,Colour separation negatives,Bromide print for the three-colour Carbro process, etc.

MATERIALS RECOMMENDED FOR SPECIFIC PURPOSES 21


COLOUR TRANSPARENCIES (35 MM. ONLY)

[lford Colour Film A. For direct photography by Photoflood lighting.WIth filter, suitable for use in daylight with only slight reduction inspeed.

llford Colour Film D. For direct photography in daylight. With filter,may be exposed to Photoflood lighting, but is then rather slow.

COLOUR SEPARATION NEGATIVES

llford. FP Special Plate. This is the best material for the preparationof contlll~ous-tone colour separation negatives for all processes. Theplate IS suitable for work froIIl:transparencies or for direct photography:under suitable conditions It IS fast enough for use in repeating-backand one-shot cameras with living models. This emulsion gives prac-tically equal gammas on the blue, green and red filter negatives whendeveloped for the same time. The characteristic curve of each negativehas a long straight line with sh?!t foot, and ~he t.hree curves agree veryclosely over the whole of their length, facilitating the production ofbalanced sets of negatives.

Liford HP3 Plate. The best material where maximum emulsion speedis essential, as in one-shot colour cameras.

Liford Special Rapid Panchromatic Plate. Recommended before the intro-duction of the FP Special Plate for continuous-tone colour separationne~atIves of subjects reqUlnr~g ~ plate of medium contrast: is especiallysuitable for the copymg of pallltlngs and subjects lacking natural contrast.

Liford Soft Gradation Panchromatic Plate. Recommended before theintroduction of the FP Special Plate for continuous-tone colour~el?aratl?n negatives of subjects with more contrast, or where the subjectt illuminated by artificial light, where strong shadows predominate andwhere a soft negative is required.

Other Ilford Plates are available for the preparation of colour separationscreen negatives for blockmaking and lithography. Details are availableon request.

Ii/fIt FilmIlford HP3 Flat Film.

Hoff FilmIlford HP3 Roll Film.

AliflirltlfreFilmllford HP3 35 mm. Miniature Film.

BROMIDE PRINTS FOR THREE-COLOUR CARBRO

1IIIIrllBromide Paper, Special for Carbro.

-


FILTERS FOR MAKING COLOUR SEPARATION NEGATIVES

Ilford Tricolour Filters are recommended for gener~l use. When workingfrom colour transparencies Ilford arrow-cut Tricolour FIlters shouldbe used (see Section Seven).

COPYINGPhotography can play a .routine part in almost every laboratory forillustrating reports, duplicating graphs, etc. .

The following materials are recommended for use when carrying outcopying work with ordinary apparatus, s.uch as a stan~ camera. Theyare grouped according to the type of subject to be copied.

Materials recommendedContinuous-tone or half-tone illustrations

Ilford Special Rapid Plate.Ilford Ordinary Plate, for greater contrast.Ilford Fine Grain Ordinary Film. .When it is desired to improve contrast by the use of ~lters or to exercise

control over the rendering of colours, the Following materials arerecommended :-

Ilford Selochrome Plate (orthochromatic). .Ilford Special Rapid Panchromatic Pla~e (panchromatic).Ilford Selochrome Film (orthochromatic).

Line drawings, typescript or printed textIlford Process Plate.Ilford Thin Film Half Tone Plate, for greater contrast.Ilford Process Film.Ilford Line Film, for greater contrast. .When it is desired to improve contrast by the use of fi~ters or to exercise

control over the rendering of colours the Following materials arerecommended :-

Ilford Ortho Half Tone Plate (orthochromatic).Ilford Rapid Ortho-line Film (or0ochromatic). .Ilford Rapid Process Panchromatic Plate ~panchromatic). .Ilford Thin Film Half Tone Panchromatic Plate (panchromatic) for

greater contrast. .Ilford Panchro-line Film (panchromatic).

RadiographsPlates: Ilford Ordinary Plate.

Ilford Special Rapid Plat.e, for slightly less contrast.Flat Film: Ilford Fine Grain Ordinary FIlm.Roll Film: Ilford Selochrome Film (orthochromatic).

Ilford FP3 Film (panchromatic).. .35 mm. Film: Ilford Fine Grain Safety Positive FIlm.

Ilford Pan F Film (panchromatic).Paper: Ilford Bromide Paper, for contact or reduced printing

from radiographs.For facsimiles by solarization: Ilford Ilfex X-ray Film.

23MATERIALS RECOMMENDED FOR SPECIFIC PURPOSES

Special copying processesWhere a considerable volume of document copying has to be done,the use of processes for which special materials and apparatus areavailable may be justified. Such processes include :-

reflex copying,camera copying direct on to paper using a document copying

camera,micro-copying,plan copying by means of reduced negatives on film,a new technique employing Ilford Autopos Paper.

For details of the materials recommended for these methods seeDOCUMENT A D PLA COPYI G.

COSMIC RAYSSee UCLEAR RESEARCH

CRYST ALLOGRAPHYSee X-RAY CRYSTAL ANALYSIS

DENT AL RADIOGRAPHYMaterials recommended

Ilford Standard Dental X-l'cryFilm. Recommended where a fast emulsionis preferred, e.g., for children and nervous patients, and for occlusalexposures without intensifying screens.

llford Standard Dental X-rcry Film No. 3a. For use with fluorescentintensifying screens for true upper occlusal exposures.

lljord Contrast Dental X-rcry Film. Recommended for subjects when afive-fold increase of exposure compared with"Standard can be tolerated.Its higher contrast and extremely fine grain lead to brilliant and virtuallygrainless results with resolution of the most minute detail.

Ilford Standard X-rq)! Film. For use with intensifying screens forextraoral work and investigation of the maxillary sinuses.

DOCUMENT AND PLAN COPYINGSee also COPYl GAlthough the copying of ordinary documents can be quite a simpleoperation, many different techniques are available and it is importantI() select the method best suited to the work in hand and to employ themost suitable materials.

The principal methods are :-(i) reflex copying,(ii) camera copying direct on to paper, using a document copying

camera,(iii) micro-copying,(iv) plan copying by means of reduced negatives on film,(v) a new technique employing Ilford Autopos Paper.

litcrature describing these methods is obtainable on request.

24 PHOTOGRAPHY AS AN AID TO SCIENTIFIC \X'ORK


REFLEX COPYI G

Ilford Reflex Contact Document Paper No. 50. For the preparation bothof negatives and positives.

Liford Reflex Contact Document Paper No. 50 Matt. Identical withDocument Paper o. 50 except that it has a matt instead of a smoothlustre surface. Recommended when freedom from glare is important.

Ilford Contact Document Paper No. 9S. A rough matt paper for makingcontact prints from reflex negatives when the copy may need to behand-coloured, e.g., for plans, maps, etc. at suitable for the preparationof reflex negatives.

lljord SI0111Contact Film. For making contact prints from reflex negativesof plans, drawings, etc., for use as intermediates in blue-print or dye-line machines.

CAMERA COPYING DlRECT ON TO PAPER

Liford Document Paper No.4. The standard paper for this work.Negatives on this paper may be re-photographed to give positives.

Ilford Document Paper No. 4T. Coated on a thinner base but otherwisesimilar to Document Paper No.4. Recommended when copies haveto be sent by ordinary post or by airmail, and for copies which mustoccupy the minimum of space.

Ilford Document Paper No. 1. Coated on a rag base but otherwise similarto Document Paper o. 4. Recommended when copies have to with-stand much handling or are required for reference over long periods.

MICRO-COPYING

Liford Micro-negOrtbo Film. For negatives of line subject. The standardfilm for this work.

Liford Pan FFilm. For negatives of continuous-tone subjects, black-and-white or coloured. Also recommended whenever shortest exposuresare necessary. Can be used with a full range of filters.

Liford Fine Grain Safety Positive Film. For positive copies of micro-negatives. Sometimes used for negatives also.

lljord Document Paper No. 60. For enlargements from micro-negatives.

PLAN COPYING BY MEANS OF REDUCED NEGATIVES ON FILM

Iljord Line Film. For all general work.Liford Rapid Ortho-line Film. For use when control over the rendering

of colours is required or when shortest exposures are essential. . Recom-mended for copying blue-prints.

j',,[ATERIALS RECOMMENDED FOR SPECIFIC PU.RPOSES

lljord Panchro-lineFilm. For use when a panchromatic film is necessary.lljord Ortho Stripping Paper. An economical alternative to film.lljord Document Paper No. 60. For enlargements from negatives.Iljord Document Paper No.7. A thicker, glossy paper. For use in pre-

ference to Document Paper To. 60 for drawings containing very finede-tail.

lljord Document Paper o. 9 A paper with a rough surface suited tohand-colouring. For enlargements from negatives of architects' draw-ings, estate plans, etc.

COPYING WITH ILFORD AUTOPO PAPER

Autopos is a new Ilford product intended primarily for making copiesdirect from draughtmen's originals and so eliminating the operationof tracing.. It 'is exp?sed in the. usual drawing office photo-printingmachines, i.e., blue-print or dye-line machines, or in vacuum frames orreflex printers, and gives direct positive images.

Autopos can be used for both reflex and contact printing and can beused very effectively for making copies by printing through originalstyped or written on one side of the paper only. .

ELECTRO-CARDIOGRAPHY (E.C.G.) ANDELECTRO-ENCEPHALOGRAPHY (E.E.C.)

The recording of the working of the heart, brain and other parts of thebody by means of electro-cardiographs and other physiological recorders.The record takes the form of a line trace on a white or black background.The sensitive materia~ may be paper, film or plate and may be movingor stationary, depending on the type of instrument being used. Copiesof records on films or plates can readily be made by printing on to paper.

Materials recommendedllford Recording Paper BPl is the standard material for instruments

1« ording on paper. Fast, blue-sensitive and suitable for both cathode1.1 a nd tungsten light sources.

llford RecordingPaper GP5 gives higher contrast than BPl but is some-\I hnt slower. It is orthochromatic and therefore very suitable for1IIIlgsten light sources.

IIjord ProcessPlate is a blue-sensitive plate for use in electro-cardiographsemploying a falling plate. Gives high contrast with well-defined lines.

l/ford Recording Film 8B21 is a high-contrast flat film similar in per-lorrnance to the Process Plate. For instruments designed or adaptedlor flat film.

l/ford Conta~tPaper, Hard, Glos!)".C.3.1P is specially suitablefor making!>hlt I and-white prints from cardiograph negatives. Upon request a11\;111Conta t Paper C.3.5P can be supplied in the 31 x6i in. size only.

25.

26 PHOTOGRAPIIY AS AN AID TO SCIENTIFIC WORK

ELECTRON DIFFRACTION

A method for the investigation of surface structure, thin films and freemolecules. A beam of electrons is directed at the object under exarrun-ation, the diffracted beam forming a pattern upon a photographicmaterial.

The materials recommended are as recommended for ELECTROMICROGRAPHY.

ELECTRON MICROGRAPHY

Electron microscopes enable objects to be examined at magni.ficationsgreater than those possible with ordinary mICroscopes. For adjustmentand focusing, an image is formed by electrons lmplngmg on a flu~rescentscreen. For exposing, this screen is replaced by a photographic plateor film.

The majority of instruments are designed to take plates, but notableresults have also been obtained on 35 mm. film.

Materials recommendedPLATES

Iljord PhotomechanicalPlate T847. Recommended for all general work.Iljord Rapid Process (Experimental) Plate. For use when high speed is

the first consideration. Both these plates are laboratory products madeto order only. Their characteristics are as follows :-

Plate Speed Speed Contrast Grainto light to electrons

Photomechanical Very Fast Extremely ExtremelyT847 slow high fine

Rapid Process Medium Very fast High Fine(Experimental)

There is no advantage in this type of work in having backing, andplates for electron micrography are therefore supplied unbacked. Plates areusually coated on normal thickness glass since the maJor~ty of commercialinstruments will accept this, but thin glass can be supplied upon request.

FLAT FILM

Ilford Recording Film 8B21.

ROLL FILM

Ilford Selochrome Roll Film.

MATERIALS RECOMME DED FOR SPECIFIC PURPOSES 27

RECORDING FILM SUPPLIED IN ROLLS

Ilford Recording Film 5Bll. 35 mm. width film has generally been usedfor this work but all standard recording film widths (16, 35, 60, 70, 120and 300 mm.) are available.

ReferencesE. M. Crook, F.M.L., Sheffield, L. V. Chilton, "Phorographic Plates for use in theR.C.A. Electron Microscope," Photo J, 858, 6-12, Jan., 1945. J. B. Le Poole, "Anew electron microscope with continuously variable magnification," Philips TechnicalReview, 9,33-45, 10. 2, 1947.

FILM SLIDESSee also FILMSTRIPS, LANTERN SLIDES

A film slide is a picture, diagram, chart, etc., on film, bound betweenglass. Film slides are frequently made from single frames of filmstripsand have an advantage over the latter in that the sequence of the framescan be varied as desired. Such slides are usually made in the 2 in. X 2 in.size.


Negatives or positives made on any film can be bound as film slides,but where positives are to be specially made for use with 2 in. X2 in.projectors the following film is recommended:-

Ilford 35 mm. Fine Grain Safety Positive Film.

FILMSTRIPS

A filmstrip is a strip of 35 mm. film bearing pictures suited for stillprojection. Such strips can be of considerable value to the scientificworker for instructional purposes.

Three distinct methods are in general use for the preparation of film-•Irips. The procedures are as follows :-Method 1. uitable when only one copy of a filmstrip 1S required, but rather1.1ho rious.

(II) Obtain negatives for each frame of the filmstrip on plate or film.Negatives of all sizes can be employed, but use of 35 mm.negatives facilitates the work. .

(b) Print by contact or projection (usually reduction) from thesenegatives on to 35 mm. positive film.

Icrhod 2I hi' IS the most flexible method and is to be recommended.

(fI) Obtain negatives for each frame of the filmstrip on plate or film.ize of negative is immaterial.


(b) Prepare a key-print on bromide paper from each negative,usually by enlargement. The prints should all be of the samesize, say, 10 in. X 12 in. or 8 in. x10 in. Diagrams for inclusionin the strip should also be prepared to this size.

(c) Photograph each of these key-prints in turn on 35 mm. negativefilm, so that each print fills one frame.

(d) Print by contact from this negative strip on to 35 mm. positivefilm. The negative can be kept to enable further prints to bemade, if required. .

Method 3Suitable only when one copy of a filmstrip is required.

(a) As Method 2.(b) As Method 2.(c) Photograph each of the key-prints in turn on 35 mm. film so

that each print fills one frame. Process the film by a reversalmethod to obtain a positive filmstrip. Instructions for thereversal processing of Ilford 35 mm. films will be supplied onrequest. •

Full information on the preparation of filmstrips is given in the book" 35 mm. Filmstrip Technique," by Peter Hansell, Ilford Limited, 1949.

Materials recommendedNo special materials are required for the preparation of the originalnegatives; any appropriate Ilford Plate or Film may be used.

Similarly any of the wide range of Ilford Papers may be used for the pre-paration of key-prints. These will normally be prepared by enlargement,and Bromide, Multigrade and Plastika Papers may be used. If, however,they are made by contact printing from large negatives, Contact Papermay also be used; rough surface papers should be avoided.

For the photography of key-prints and the printing of the final filmstripthe recommended materials are as follows ;-For the preparation of 35 mfll. negatives from kry-prints (Method 2).

The materials recommended are grouped according to the type ofkey-print to be copied.

(i) Continuous-tone or half-tone illustrations, including ordinaryphotographs.Hford Pan F Film.Ilford Fine Grain Safety Positive Film (if care is taken duringdevelopment to avoid excessive contrast).

(ii) Line drawings, typescript or printed text.Ilford Micro-neg Ortho Film.Ilford Fine Grain Safety Positive Film.

Ilford Pan F Film may be used for subjects of type (ii) when it is desiredto prepare a single negative of a filmstrip which also includes subjectsof type (i).

Panchromatic or orthochromatic films are to be preferred if it is desiredto exercise control over the rendering of colours.

MATERIALS RECOMMENDED FOR SPECIFIC PBRPOSES

For the preparation of 35 fIIfII.positives i?Ydirect reversal (Method 3)Ilford Pan F Film.Ilford Fine Grain Safety Positive Film ..Pan F is to be preferred if it is desired to exercise control over the

rendering of colours.Note.-Pan F is primarily intended as a negative film and is coated on

a base which is dyed grey for anti-halation purposes. This base colour,which cannot be removed, has the effect of reducing the light trans-mitted by the film to about 60 per cent. of the incident light. FineGrain Safety Positive Film is coated on a clear base.For printing filmstrips from negatives (Methods 1 and 2).Whether this is done by contact or by projection printing, the materialrecommended is ;-Ilford Fine Grain Safety Positive Film.

For estimating exposure in printing, and for making prints for referencepmposes, the following paper may be used;-Ilford Bromide Paper, Normal, Glossy, Single Weight, 35 mm. perforated.

FINE GRAIN

Fine grain emulsionsSee HIGH RESOLUTION

Fine, grain developmentSee page 52-Fine Grain Development.

FLASH PHOTOGRAPHY

Including the use of flash-powder, flash bulbs, electronic flash tubes,and high-intensity sparks.

Materials recommendedFor photographing objects which are moving with extreme speed, forexample, projectiles, the most sensitive materials are recommended.I J P3 Plate stands first for this purpose, closely followed by HP3 Film.h>r objects moving less rapidly the permissible time of exposure is longenough to allow slower, fine grained materials to be used.

For medical photography with electronic flash Selochrome Plate givesvery good colour contrast.

Negatives exposed by electronic flash tend to be flat unless full develop-111 'Ill is given. Development times 50 per cent. above those required forIIl<linary. work are generally advised.

FLUORESCENCE PHOTOGRAPHY(FL UOROSCOPY)

11LTRA-VIOLET PHOTOGRAPHY

29

Ii

30 PHOTOGRAPHY AS AN AID TO SCIE 'TIFlC WORK

FL UORESCENT SCREEN PHOTOGRAPHY(FL UOROGRAPHY)

See CATHODE RAY TUBE TRACESCI E RADIOGRAPHYMASS MINIATURE RADIOGRAPHY

GAMMA-RAY RADIOGRAPHYRadioactive substances such as radium and radon form easily portablesources of very penetrating radiation and are useful for the radiographyof heavy and complicated subjects,

For the materials available for this work see I DUSTRIAL RADIO-GRAPHY.

GRATICULE MAKINGPhotographic methods of making graticules include those in which thefinal image is made on a photographic emulsion and others using aphotomechanical resist in which the final image is etched on glass,Most processes employ large black-and-white drawings as originals,reduction being obtained in one or more stages.

Materials recommendedThe following Plates may be used for negatives and, where photographicimages are required, for the final positives.

Iljord Thin Film Haf! Tone Plate. For scales and coarser graticules.Iljord High Resolution Plate. For very fine graticules.

ReferenceP. C. Smethurst" Microphotography and graticules," Phot.]., 84, 147~151. May, 1944.

HIGH RESOLUTIONIncluding all work where the highest resolving power is essential.

Materials recommendedIljord High Resolution Plate. Specially prepared to give maximum

resolution.HIGH-SPEED PHOTOGRAPHY

See FLASH PHOTOGRAPHY

INDUSTRIAL CINEMATOGRAPHYSee CINEMATOGRAPHY

INDUSTRIAL RADIOGRAPHYRadiography has innumerable applications in industry, and the X-rayResearch Department of Ilford Limited has made a special study of theproblems involved in this work. A range of special materials has beendesigned to meet the varied needs of the industrial 'radiographer.

MATERIALS RECO:1lfMENDED FOR SPECIFIC PURPOSES 31

Materials recommendedThe materials available are listed below. Fuller descriptions of theircharacteristics and applications are given in the booklet" Ilford X-rayFilms and Screens for Industrial Radiography."

Liford Industrial X-rcry Film A. This film is primarily intended as anextremely fast film for use with intensifying screens, but it does alsoserve as a fast, medium contrast film for non-screen or lead screenexposures.

Iljord Industrial X-t·cryFilm B. A fast, high-contrast film for use withoutscreens or with lead screens.

Iljord Industrial X-rcryFilm C. A non-screen or lead screen film requiringabout three times the exposure of Film B, but having considerablyhigher contrast and very fine grain. Ideal for the detection of fine cracksin ferrous welds and for all subjects where the highest possible resolutionis required.

Ilford Standard X-rcry Film. This is primarily a medical film though ithas its applications in industrial work. It should be used only withintensifying screens, when it has less speed than Film A but highercontrast.

Liford X-ray Paper. For use with or without intensifying screens.

INFRA-RED PHOTOGRAPHY

The property of infra-red rays of penetrating media opaque to visiblerays has been put to practical use in photography in a number of ways.These include:-

Penetration of haze in outdoor photography,Penetration of tissues opaque to ordinary light,Differentiation of materials which appear identical to the eye,Deciphering of old or defaced documents,Photography in the dark,Medical photography, e.g., to show veins, subcutaneous con-

ditions, pupil dilatation and for post-mortem specimens andphotomicro graph y.

To obtain unusual effects in pictorial photography,Photographic measurement of temperature.

Although these applications have at times aroused a great deal of interest,Ihe volume of work involved has in most cases been very limited. Themost important single use of infra-red materials to-day is probably inIh preparation of the black printer negative in four-colour screenprinting, and the Ilford Infra-red Process Plate is intended for this work.

Materials recommendedIljord Infra-red Process Plate. A relatively slow plate of high contrast,

III" the preparation of the black printer negative in four-colour screen1'lll1ting-.


Despite its high contrast this plate may also be of use in some of the otherapplications listed above: in case of doubt experiment should be madeto determine its suitability.

ReferencesS. O. Rawling, " Infra-red Photography," Blackie.\,(/ali:erClark, " Photography by Infra-red," Macmillan.

LANTERN SLIDES

See also FILM SLIDES

Slides may be made by contact or projection printing from negativesor, in the case of line drawings, typescript or printed text, negativesmade in the camera can be bound up as slides.


FOR CONTACT PRINTING

Ilford Contact Lantern Plate. A relatively slow plate which may behandled by weak artificial light. The very high contrast of this platemakes it particularly useful for line diagrams and for saving underexposednegatives. Normal development in ID-36 produces a blue-black image.

FOR PROJECTION PRINTING

Ilford Special Lantern Plate. Available in three grades, Soft, Normal andContrasty. Normal development in ID-36 gives black tones.

Special Lantern Plates may also be used for contact printing, but forthis purpose they will require an exposure of only about one-hundredthof that required for the Contact Lantern Plates normally recommended.

FOR EGATIVES OF LINE SUBJECTS

Iljord Process Plate.Iljord Thin Film Halj Tone Plate, for greater contrast.When it is desired to improve contrast by the use of filters or to exercise

control over the rendering of colours, the following are recommended :-Iljord Ortho Half Tone Plate.Iljord Rapid Process Panchromatic Plate.Iljord Thin Film Half Tone Panchromatic Plate, for greater contrast.Ilford Lantern Plates are supplied in sizes to suit all standard projectors,

miniature projectors and stereoscopes. The other plates recommendedare obtainable in the standard 3i- in. X 3! in. size.

MASS MINIATURE RADIOGRAPHY

This is an indirect method of producing a radiograph by photographingwith a miniature camera the radiographic image on a fluorescent screen.It owes its reliability in the medical field in this country very largely toresearch in the Ilford Radiographic Department.

MATERIALS RECOMMENDED FOR SPECIFIC PURPOSES


Ilford HP X Filr». A very fast, panchromatic film of medium contrast.Supplied in rolls of 35 mm. and 70 mm. width.

Iljord Recording Film 5G91. An alternative to HP X when greatercontrast or non-panchromatic material is required. Primarily intendedfor non-grid techniques.

Also recommended when a blue screen is employed.

References

i\ledical Research Council SpecialReport, SeriesNo. 251-l\Iass Miniature Radiographyof Civilians, H.M. Stationery Office.

MASS SPECTROGRAPHY

In the mass spectrograph a photographic plate is used to record theimpinging upon it of positively charged, rapidly moving atoms detachedfrom the material under examination by a cathode-ray stream. The pathof the atoms is deflected by electrical and magnetic means, and thecharged atoms are spread out in spectral series and on striking theemulsion render it developable. The detection of isotopes is madepossible by this method.


Iljord Q PlatesIn these plates, the first coatings of which were specially produced for

mass spectrography, the silver halide grains project from the surfaceand absorption by the gelatin is reduced to a minimum. Q Plates aremade in three speeds-Ql Slow, Q2 Medium, Q3 Fast. Grain size andcontrast of the plates are in order of their speeds, Q1 being the finestgrained and most contrasty (see also page 5).

ReferenceF. \Y/. Aston, Proc. Roy. Soc., A., 126, 511: A, 130, 302: A, 132,487.

MEDICAL PHOTOGRAPHY

1\ wide variety of work falls under this heading. Suggestions are givenI'or the materials likely to be of most use in certain instances, but these.1 re by no means exhaustive. For subjects such as COPYING and INFRA-I{ ED PHOTOGRAPHY, which are of interest to others besides themedical photographer, see the appropriate heading elsewhere. in thiscction.

33

34 PHOTOGRAPHY AS A AID TO SCIE TIFlC WORK

Materials recommendedPlates Flat Films Roll Films

(1) For stlijects 1Vithslight red,yello1V, or brownmarkings to be recordedas contrasting tones

Selochrome Selochrome SelochromePress Ortho Hyperchromatic *BP3

Series 2 *FP3(2) To demonstrate shape, e.g. posture, skeletalcharacteristics, deformities. Where there aremarked differences in intensiry of colour

*HP3 *HP3*Soft Gradation *FP3

Panchromatic*Special Rapid

Panchromatic*With appropriate filters.(3) For records in. natural colourFor medical photography employing Photoflood lighting, Ilford ColourFilm A (35 mm. only) may be used. No filter is required.

35 mm. Fi/ms

*HP3*FP3*Pan F

*HP3*FP3

*HP3*FP3*Pan F

MEDICAL RADIOGRAPHYThe applications of X-ray photography in medicine are many andvaried. They include the radiography of soft and hard, or hollowstructures demonstrated with or without contrast media and usingfrom 40 to 100kVp.

Materials recommendedThe materials available are li ted below. Fuller descriptions of theircharacteristics and applications are given in the "Ilford Catalogue ofX-ray Materials and Accessories."

Iljord Standard X-ray Film. A general-purpose medical film for use witbsalt intensifying screens, under which conditions it gives very highcontrast. This film may also be used without screens for work on tbeextremities.

Iljord Red Seal X-rcry Fil»r. A special screen-type medical film of twicethe speed, and of slightly softer gradatioJil than Standard X-ray Film.

Liford Iljex X-ray Film. A non-screen film of high speed and highcontrast.

Iljord X-rcryPaper. A useful and relatively cheap adjunct to X-ray Films.Is particularly useful for preliminary or exploratory exposures, or whererepeat exposures are required. Also recommended whenever directnegative prints are preferred. For use with or without intensifyingscreens.

ReferenceK. C. Clark, "Positioning in Radiography," Ilford Limited.

MATERIALS RECOMMEI DED FOR SPECIFIC PURPOSES 35

METALLOGRAPHY

The photomicrography of metal specimens, usually polished and etched,in the study of the internal structure of metals and their alloys.

Materials recommendedIljord Chromatic Plate. The standard plate for this work. This is an

orthochromatic plate of medium to high contrast. Yellow and greenfilters can be used advantageously with this plate.

Iljord Rapid Process Panchromatic Plate. A panchromatic plate of slightlyhigher contrast than the Chromatic Plate. Can be used with a full rangeof filters.

ReferencesR. H. Greaves and H. Wrighton, " Practical Microscopical Metallography," Chapmanand Hall, Ltd.C. H. Desch, " Metallography," Longmans, Green and Co.

MICRO-COPYINGSee DOCUME T AND PLAN COPYING

NUCLEAR RESEARCH

The investigation of the behaviour of atomic particles by examining thetracks they make in photographic emulsions.

Alpha-particles, neutrons, protons, cosmic rays, etc., are all capable ofproducing tracks of silver particles in suitable emulsions when theseare developed. The length and shape of the track and the spacing of theseparate developed grains provide an indication of the nature of theparticle.

In recent years the application of the photographic emulsion to theinvestigation of atomic disintegration has received an impetus fromthe preparation by Ilford Limited of special emulsions for this work.

Materials availableIljord Nuclear Research Plates. These plates have found wide application

since their introduction early in 1946. They have been used by physicistsall over the world and have played a leading part in work on cosmic rays.The standard types of uclear Research Emulsions are described onpages 5 and 6 but further details are contained in a special leaflet availableon application.

PHOTO-ELASTIC STRESS-ANALYSIS

In this technique for the examination of stress-distribution a model ofthe object to be tested is made in a transparent material and viewedbetween crossed polarizing screens. A pattern of light and dark bands,which mayor may not be coloured, is seen and can be examined visuallyor recorded photographically.

36 PHOTOGRAPHY· AS AN AID TO SCIENTIFIC WORK

Materials recommendedFOR RECORDS IN BLACK-AND-WHITE

A large variety of plates and films are quite suitable for this work.Generally a material of fairly high contrast will be best. Such materialsare relatively slow, but if the subject is stationary this will not normallybe a disadvantage. The following materials are of this type and arerecommended for general use.Panchromatic:. llford Rapid Process Panchromatic Plate.

Ilford Panchro-line Flat Film.Orthochromatic:

llford Chromatic Plate.llford Rapid Ortho-line Flat Film.

.If the exposures required with these materials are inconveniently long,faster materials may be used, but these will inevitably result in somereduction in contrast. The following materials are recommended whenthe shortest exposures are essential:Panchromatic:

Ilford HP3 PlateIlford HP3 Flat Film.

Orthochromatic:Ilford Selochrome PlateIlford Selochrome Flat Film.

Note.-For this work panchromatic plates and films have a wider rangeof usefulness than orthochromatic materials. Panchromatic materialsmay be used with any of the normal monochromatic or white lightsources. Orthochromatic materials are suitable for use with mono-chromatic sources comprising the green lines of the mercury arc, butare not suitable for use with the yellow mercury line or with sodiumlamps.

FOR RECORDS IN COLOUR

Ilford Colour Film A (35 mm. only) may be used for the preparation ofdirect colour transparencies. A Photoflood bulb should be used as thelight source.

Reference"Photo-elasticity," E. G. Coker, L. G. . Pilon, Cambridge University Press, 1930.

PHOTOGRAMMETRYAerialSee AERIAL PHOTOGRAPHY

T erres trialSurveying by photography, often with a photo-theodolite.

MATERIALS RECOMMENDED FOR SPECIFIC PURPOS ES

Materials recommendedThere is no standard plate for this work, but plates of fairly high contrastare usually employed. Plates supplied in the past have included F.P.

pecial and orthochromatic process plates. For the Wilde TheodoliticCamera, plates can be supplied measuring 10 cm. X 15 cm., 1.8 to 2.2mm. thick, specially selected for flatness with three edges smoothedand one left as cut.

The recording by photographic means of magnified images of minuteobjects. Records may be made in black-and-white or in colour.

Ilford Limited supply not only the sensitive materials for this workbut also a wide range of colour and neutral filters catering for all needsof the microscopist (see Section Seven). The plates and films recommendedfor various types of work are listed below.

Materials recommendedPlates

Non-coloured objectsOrdinary

PHOTOMICROGRAPHY

Flat Films

Fine GrainOrdinary

Pond life, and objects containing milch greenChromatic Selochrome

RapidOrtho-line

Stained sectionsSpecial Rapid Panchro-line

Panchromatic RapidRapid Process Ortho-line

PanchromaticLiving bacteria

HP3 HP3

For Jvork in the ultra-oiolet regionProcessZenith

ProcessFine Grain

OrdinaryFor records ill natura! colour

35 mm. Filflls

Fine GrainSafety Positive

Pan FMicro-neg

Ortho

Pan FMicro-neg

Ortho

HP3

Fine GrainSafety Positive

HP3

Colour Film ANote.- With achromatic objectives best results' are obtained with agreen light source and orthochromatic or panchromatic materials.Negatives on non-colour-sensitive materials are not so sharp even whenfocusing is done with a blue filter. Apochromatic objectives give equallygood results with all colours.

PLAN COPYINGSee DOCUMENT A D PLA T COPYING

.",7


POWDER SPECTROGRAMSSee X-RAY CRYSTAL ANALYSIS

RADIOGRAPHYSee CINE-RADIOGRAPHY

DENTAL RADIOGRAPHYINDUSTRIAL RADIOGRAPHYMASS MINIATURE RADIOGRAPHYMEDICAL RADIOGRAPHY

RECORDINGSee also CATHODE RAY OSCILLOGRAPHY, ELECTRO-CARDIO-GRAPHY (E.CG.) and ELECTRO-ENCEPHALOGRAPHY (E.E.c.)Scientific instruments employing photographic means for recordingare many and varied. The choice of the most suitable material dependson a number of factors, including :-

intensity of light source,spectral emission of light source,exposure permissible,movement of the trace relative' to the sensitive material.

While it is nqt practicable to publish detailed recommendations for eachof the instruments in use to-day, Ilford Limited will be glad to advise inindividual instances. A general list of the materials specially suited tothis work is given below.Materials recommended

•

FILy[S

Liford RecordingFilm 8Rl01. A very fast, panchromatic film of mediumcontrast. Supplied as a flat film.

Liford RecordingFilm 8B2l. A relatively slow, non-colour-sensitive filmof high contrast and very fine grain. Supplied as a fiat film.

Ilford RecordingFilm 8B01. A relatively slow, non-colour-sensitive filmof high contrast and still finer grain than 8E21. Supplied as a flat film.

Ilfori: Recording Film 5Rl0l. Similar to 8Rl0l, but supplied in rolls.Ilford Recording Film 5G91. .A very fast, orthochromatic film of high

contrast. Supplied in rolls.Liford RecordingFilm 5B52. A fast, non-colour-sensitive film of medium

contrast on a permanently dyed orange base, designed to reduce halationand irradiation to an absolute minimum. Pre-hardened to withstandprocessing at high temperatures. Supplied in rolls.

Ilford Recording Film 5Bll. Intermediate in characteristics between8E21 and 8E01, and supplied in rolls.

PAPERS

Ilford RecordingPaper GP5. A relatively slow, orthochromatic paper ofhigh contrast. Supplied in rolls.

llfordRecording Paper BPl. A fast, non-colour-sensitive paper of mediumcontrast. The standard material for most instruments making recordson paper. Supplied in rolls.

MATERIALS RECOMMENDED FOR SPECIFIC PU.RPOSES 39

PLATES

The use of plates for recording is not as widespread as that of films andpapers, but where for any reason the use of plates is desirable, standardIlford Plates are recommended as follows :-Panchromatic

Ilford Rapid Process Panchromatic Plate. A medium speed plate ofhigh contrast.Orthochromatic

Ilford Ortho Half Tone Plate. A slow plate of very high contrast.Ilford Press Ortho Series 2 Plate. A very fast plate of medium contrast.

Non-colour-sensitiveIlford Special Rapid Plate. A relatively slow plate of medium contrast.

OrderingFull details must be given when recording materials are ordered. Detailsof packings available and directions for ordering will be supplied onrequest. Standard widths for rolls of films and paper are 16 (not paper),35, 60, 70, 120 and 300 mm.

REFLEX COPYINGSee DOCUMENT AND PLAN COPYING

SEPARA TION NEGATIVESSee COLOUR PHOTOGRAPHY

SPECTROGRAPHY

Materials recommendedFor 1vork in the ultra-violet andblue region of the spectrum (2300-5200A).

Plate

II Increasing

t

Approximate relativesensitivities in the

ultra-violetGrain size

Thin Film Half-toneProcessOrdinarySpecial RapidZenith Super-sensitive

12.547

25

•Ilford Ordinary Plates, of medium speed, contrast and grain are commonlyused. If greater sensitivity is needed, this may be obtained, at the expenseof somewhat lower resolving power, by using Special Rapid, or, forextreme speed, Zenith Super-sensitive Plates. If exposure conditionspermit, increased contrast and resolution may be obtained from Processand Thin Film Half Tone Plates.

40 PHOTOGRAPHY AS A AID TO SC]EN TlFlC WORK

For work at longer wavelengths:

Speed I Contrast ApproximatePlate Range Grain relative

(to the visible sensitivitiesspectrum) in U. V..

Ortbocbromatic :Chromatic 2300- Slow Medium Fine 5

5900A I to highSelochrome 2300- Fast . Medium Medium 8

5900AI

Panchromatia :I Very highThin Film Half 2300- Slow Very fine

Tone Panchromatic 6700ARapid Process 2300- Medium High FinePanchromatic 6500A ,Special Rapid 2300- Medium Medium FinePanchromatic 6500A

The choice of plate will depend on the work in hand. For general work,including the red part of the spectrum, Rapid Process PanchromaticPlates are recommended.

Plates for special purposes:Ilford Infra-red Process Plate

Slow }High contrast For work in the infra-red region of theVery fine gramRange: 2300-5200A spectrum.

and 7400-8800AIlford Long-Range-Spectrum Plate

Medium speed I For taking spectrograms covering on

F~lgh co~trast \.one plate the whole range of the spectrumwe graw j fl' 1 inf . dRange: 2300-88001\ rom u tra-vio et to near I ra-re.

Ilford Q PlatesRecommended for ultra-violet spectroscopy below 2300A whereabsorption by the gelatin is an important factor.

These emulsions have a low gelatin content and the silver halide particlesproject from the surface .. As a result they must be handled at all stageswith extreme care. Three types of plates are available-Ql, Q2, and Q3 ;Ql is the slowest type and Q3 the fastest. Grain size and contrast of theseplates are also in order of their speeds, Ql being the finest grained andmost contrasty (see also page 5). Q Plates are not supplied backed.

MATERIALS RECOMMENDED FOR SPECIFIC PURPOSES 4]

ReferencesF. C. Chalklin, " Intensity measurements in the very soft X-ray region." Proc. Roy.Soc., A., 194,42-62,1948.

H. T. Shirley,E. Elliot, Joyce Meeds, " Spectrographic analysisof low-alloysteel-A statistical examination of sources of error." Journal of the Iron and Steel JnstNovember, 1947,391-409. .,

SULPHUR PRINTING OF STEELThe presence a~d .distribution of sulphides segregated in steel ingotsprovide an indication of the stage of crystallization of the steel. If aweak sulphuric acid solution is applied to the polished surface of thesteel and. a sheet of sensitive paper applied to the surface, hydrogensulp~lde IS ~elease~ and cause~ lo~al ~rown stains on the paper. Theseprovide an indication of the distribution of the sulphides.Materials recommendedIfjord Bromid~ PCtpe~,Single Weight, Matt or.Semi-Matt. The contrast gradeof the paper ISnot Important. Paper required solely for this work shouldbe ordered simply as "Bromide Paper for Sulphur Printing."

SURVEYINGSee PHOTOGRAMMETRY

TOPOGRAPHYSee AERIAL PHOTOGRAPHY

PHOTOGRAMMETRY

UL TRA- VIOLET PHOTOGRAPHYThere are two meth?ds of using ultr~-viole.t radiation for photography.

~he first method ISto ~emove all visible light and to use only ultra-violetradiation to record the Image. To ensure the passage of the maximumamount of ultra-violet radiation it is necessary to use a quartz lensinstead of the usual glass lens of the camera, although useful results canoften be obtained with ordinary lenses.

The second and more usual method is to photograph the visible fluores-cnce of the subject cause~ by ultra-violet radiation falling upon it. The

camera lens IS covered WIth an ultra-violet-absorbing filter so that onlyrh fluorescence is recorded. This technique is known as "Fluoroscopy."Materials recommendedPlates

llford Ordinary Plate, orllford Zenith Super-sensitive Plate, where shortest exposures are

(\ sential.foi//8r.r

Ilford Limited supply two filters of particular application in this work.( )1\ • a~sorbs ult:a-violet radiation and transmits visible light; the otherII.IIlSITIltSultra-violet but absorbs the visible spectrum (see Section Seven).

42 PHOTOGRAPHY AS AN AID TO SCIE TIFIC WORK

SECTION FOURWELDINGSee also INDUSTRIAL RADIOGRAPHY

Photographs of welds are sometimes required for the training of welders,etc.

Materials recommendedAs the subjects are stationary, relatively slow materials can normallybe used with advantage.

Iljord Special Rapid Plate. A relatively slow, non-colour-sensitive plateof medium contrast.

Iljord Selochrome Plate. A fast, orthochromatic plate.

Determining exposure time

X-RAY CRYSTAL ANALYSIS Exposure time in negative making is usually assessed in one of threeways:

Materials recommendedIljord Iljex Film. A fast, non-screen film of high contrast and medium

grain size.Ilford Industrial X-rqy Film C. Where the increased exposure time can

be tolerated, Industrial C, with one-third the speed of Ilfex, may be.• found to give better results by virtue of its higher contrast and smaller

grain size. It is particularly suitable where photometric measurementsare required.

Iljord Standard X-rqy Film.Ilford Industrial X-rqy Film A.

These films may be used when the camera design and the purpose ofthe investigation permit the use of intensifying screens for shorteningexposures.

(i) by making a series of test exposures,(ii) by using exposure tables or calculators,(iii) by use of an exposure meter.

The relative merits of these methods are discussed below.

MAKING A SERIES OF TEST EXPOSURES

Recommended for all work where exposure is critical, especially whenusing high-contrast materials. Has particular application when workingby artificial light, which can be readily controlled. When the exposurehas been determined for a given set of conditions it can be used repeatedlyprovided the disposition of camera, subject, lamps, etc., is unaltered.

Work in which exposures are normally determined in this way includes:Copying,Metallography,Photomicrography.

In copying, as a basis for such trial exposures, use may be made ofexposure calculators or tables (see below).

X-RAY PHOTOGRAPHYSee CI E-RADIOGRAPHY

DENTAL RADIOGRAPHYINDUSTRIAL RADIOGRAPHYMASS MINIATURE RADIOGRAPHYMEDICAL RADIOGRAPHY

EXPOSURE TABLES AND CALCULATORS

X-RAY POWDER ANALYSIS

See X-RAY CRYSTAL A ALYSIS

Suitable for general indoor and outdoor photography. Many publishedtables and calculators are available. Ilford tables, published in the••Ilford Manual of Photography," include:

exposure tables for general photography in daylight;exposure tables for general photography in artificial light;exposure tables for copying in artificial light.

Daylight tables take into account such factors as speed of photographicmaterial, date and time of day, type of weather and nature of subject.A rtificial light tables are related to speed of material and light intensity,dl~tanee and direction.

44 PHOTOGRAPHY AS A AID TO SCIE TIFIC WORK

Tables have similarly been evolved for use in radiography and are tobe found in "Positioning in Radiography" and the "Ilford X-rayExposure Record."

EXPOSURE METERS

Three exposure meters are obtainable from Ilford Limited.(i) Iljord Exposure Meter, Model C. A general purpose photo-

electric exposure meter which is simple in use and smallenough for the pocket.

(ii) Weston Master Universal Exposure Meter, Model S74/715. Aphoto-electric exposure meter noted for its long range ofsensitivity.

(ill) S. E.I. Exposure Photometer. A new precision instrument forthe determination of exposures in general photography,reversal processes, copying, enlarging and for accuratemeasurements of transmission and reflection densities,illumination levels and other factors of interest to photo-graphers and illuminating engineers.This instrument possesses two outstanding advantages overmost photographic exposure meters: (1) it can be used tomeasure the brightness of very small areas in the scene, thespot in the field of view sub tending an angle of only iO, and(2) the range of brightness which may be measured is amillion to one, accommodating dark surfaces in interiorsand brilliantly lit skies. The S.E.I. Exposure Photometerhas already found many uses in scientific work.

SPEED SYSTEMS

When an exposure table, calculator or meter is used, reference must bemade to the speed of the photographic material in use. A number ofdifferent ways of expressing the speed of negative materials are in generaluse. The systems employed on products made or distributed by IlfordLimited are as follows:

Speed systemIlford Speed Group

Where employedPlate and film boxesIlford Exposure Meter, Models A, B,

and CPlate and film boxesIlford Exposure Meter, Model CS.E.I. Exposure PhotometerWeston Master Universal Exposure

Meter, Model S74/715exposure meters calibrated in Scheiner

*Ilford SpeedIndices

B.S.I. DegreesWeston Speed

Ratings*Also suitable for use with

Degrees.

DETERMINING EXPOSURE TIME 45

EXPOSURE BY ARTIFICIAL LIGHT(Tungsten filament lamps)

The speed ratings printed on the boxes of Ilford Plates and Films a~edaylight ratings. When using a photo-electnc exposure meter III

artificial light, the daylight rating may be employed and the exposureindicated by the meter increased by the appropnate factor from column1 of the table below. If the rating employed is a~ Ilford Speed In~ex orother logarithmic speed index the same correction may be applle~ bysubtracting the appropriate figure in column 2 below from the daylightvalue ..

Type of material (1) (2)

Hypersensitive panchromatic materials(HP3FP3FP Special)

x 1{

_-ormal panchromatic materials(Special Rapid Panchromatic

oft Gradation PanchromaticPan F)

xlt

Orthochromatic materials(ChromaticCommercialOrtho,Selochrome,Press Ortho Series 2,Hyperchromatic)

x2

Ordinary materials(Ordinary,Soft Ordinary,Special Rapid,Zenith Super-sensitive)

x4

SPEED CONVERSION TABLE

When the speed of a particular material is known in one system andneeded in another, the figure required can be read directly fromfollowing table :-

46 PHOTOGRAPHY AS A AID TO SCIE TIFIC WORK

Relative Ilford iplforj B.S,!. .Amer. DIN H& D Amer.Speed Group I /e * Degs. Scheiner /70 Brit. G.E.naex

ASA Well-No. TVeston comet

1 A16° 15° 11° 6° 80 3 2.5 2 2/317° 16° 12° 7° 100 4 3 .5 1/218° 17° 13° 8° 125 4.5 4 3 -

19° 18° 14° 9° 160 6 5 4 1/320° 19° 15° 10° 200 7.5 6 5 1/421° 20° 16° 11° 250 9 8 6 -

22° 21° 17° 12° 320 12 10 8 1/623° 22° 18° 13° 400 15 12 10 1/824° 23° 19° 14° 500 18 16 12 -

25° 24° 20° 15° 640 24 20 16 1/1226° 25° 21° 16° 800 30 25 20 1/1627° 26° 22° 17° 1000- 36 32 24 -

28° 27° 23° 18° 1250 48 40 32 1/2429° 28° 24° 19° 1600 60 50 40 1/3230° 29° 25° 20° 2000 75 64 50 -

31° 30° 26° 21° 2500 100 80 64 1/4832° 31° 27° 22° 3200 120 100 80 1/6433° 32° 28° 23° 4000 150 125 100 -

34° 33° 29° 24° 5000 200 160 125 1/9635° 34° 30° 25° 6400 250 200 160 1/12836° 35° 31° 26° 8000 300 250 200 -

2 B

4 C

8 D

16 E

32 F

64 G

*Also Scheiner Degrees, British and Continental.tAs used in We/kome Calculators prior to 1950.There is no fixed conversion between the various systems, except B. .1. Degrees andA.S.A.Numbers, because they are based on different criteria, but speed ratings derivedfrom this table will, in general, be found reliable in practice, although they may notalways exactly agree with manufacturers' recommendations.

With speeds given in "degrees," e.g., Ilford Speed Indices and British StandardDegrees, an increase of 3~ in the speed index means a doubling of photographic speed,corresponding to a halving of the exposure required.

With speeds given as plain" numbers," e.g., Weston Ratings and American StandardSpeed Numbers, a doubling of the speed number means a doubling of the photographicspeed.

In the Ilford Speed Group System materials in anyone group are approximately twiceas fast as those in the preceding group and half as fast as those in the group that follows.This system only takes into account speed differences of the order of x2, but givesspeed values quite close enough for ordinary black-and-white photography.

A table of speed ratings for Ilford Plates and Films appears on page 14.

iI

SECTION FIVE

Safelights

Darkroom illumination must be considered in relation to the particularsensitive materials to be handled. With the slower and less colour-sensitive materials the aim should be to achieve the highest level ofillumination consistent with safety, and this means careful choice andpositioning of safelights, With fast panchromatic materials no light atall should be used, development being strictly to time and temperature.A dark-green safelight may be used for illumination of the darkroomclock, for example, but the direct light should not be allowed to fallupon the sensitive material.

Ilford Limited supply darkroom lamps and safelights for all require-ments. The complete range of Ilford Safelights is as follows:

SafelightColour For use with

Number I_N_am_e_I.

I_

901 VS Yellow Contact Paper, Reflex Contact Doc-umentPaper, Contact Lantern Plates,Contact Film, and other very slow,non-colour-sensitive materials.

902 I S Light brown Bromide Paper, Plastika, Multi-grade and other SI01V, non-colour-sensitive materials.

903 I Infra-red

Yellow-green Infra-red plates.

904 Dark brown Process Plates, Process Films,Special Lantern Plates and otherfast, non-colour-sensitive materials.

F

Continued 0/1 nex ~S.\."~<::~~~JBRA~{;):Yl

'-5'''---4 .. t... ~""'="'

48 PHOTOGRAPHY AS AN AID TO SCIENTIFIC \'(IORK SAFELlGH TS

Safe/ight

1i;mber I NameColour For use with

905 X Olive green X-ray Films and Paper, 1 ot suitablefor. use with colour-sensitive

I materials.

906 I Iso Ruby red Orthochromatic materials.

907 G Dark green Very slow, panchromatic plates andI films.I

908I

GB Green-blue All panchromatic plates and films

Iexcept the very slowest. Althoughdesigned for the maximum possible

I efficiency this safelight must be usedwith extreme care. Hypersensitivematerials must not be exposed toits direct light for any appreciablelength of time.

909 I Bright Green

IDesensitized panchromatic plates

I green and films.

STANDARD SIZES

Sizes normally supplied are as follows :-

Inch5 in. X 7 in.8 in. X 10 in.

10 in. X 12 in.

Metric13 em. X 18 cm.16 cm. X 21 ern,20 cm. X 25 cm.Other sizes are available to order.

CARE AND USE OF SAFELIGHTS

Ilford Darkroom Safelights consist of glass coated with coloured gelatin,passing light of the quality giving maximum brightness consistent with

49

safety with the particular sensitive materials with which they are intendedto be used. The choice of light source for illuminating the safelightand the ventilation of the darkroom lamp are both important.

The bulb should be bright enough to give ease of working but not sobright as to render the light unsafe nor so hot as to damage the gelatinfilter. The safelight should never be allowed to become so hot that it isunbearable to the touch. In many darkroom lamps the light from thebulb reaches the safelight direct; for lamps of this type a diffuser shouldbe incorporated as part of the safelight. In some other darkroom lamps,however, the bulb is hidden behind a ba.fle and the light strikes thesafelight indirectly; for these, the safelights may be used with diffusersor without (i.e. clear) according to circumstances. Clear safelights arerecommended for darkroom lamps which have a viewing panel behindthe safelight. Normally Ilford Safelights are supplied bound up withdiffusing screens, but on request may be supplied in the clear form.

As a rule, the bulb used in a darkroom lamp should be of as Iowa poweras possible, for example, for darkroom lamps in which there is no lightbaffle and which are used to illuminate sensitive materials directly, a15W bulb should be used. If such a lamp is used to illuminate a roomby an indirect method, for example, by reflection from the ceiling, a 25Wbulb may be necessary. For darkroom lamps in which internal baHesare used to distribute the light before it emerges into the room, morepowerful bulbs, 25W or even 40W, may be required, but in the choiceof bulb care must be taken that the safelight will not be overheated.

Whenever new safelight illumination is installed it should be tested byexposing a piece of the material to be handled for a time at least equalto that for which it will be exposed in practice and at the same distancefrom the lamp. A coin or other opaque object should be laid on thesurface of the material so as to provide for comparison a sharply definedregion of unexposed surface. If on development the exposed surfaceappears at all darker than the shaded portion, the illumination is unsafeand must be reduced. Either a bulb of lower power should be fitted orthe distance increased. It is of course possible that the fog may be dueto white light if blinds or light traps are imperfect.

Care should be taken that safelight screens are not allowed to becomedamp or contaminated by processing solutions.

ILFORD DARKROOM LAMPS

llford Darkroom Lamps are described in the first column of the table onpage 50 and the Safelights and bulbs recommended for use with them arelisted in the other columns of the table. All the lamps are exceptionallywell ventilated and with the recommended bulbs no trouble throughoverheating will be experienced. Darkroom Lamps and Safelightsshould be ordered separately.

50 PHOTOGRAPHY AS Al AID TO SCIENTIFIC WORK

SafelightDarkroom Lamp

IBulb

Size Type

No.2A lamp of pyramid form held at 8xl0ins. With For directthe point of balance by a stirrup i diffuser illumination:which can be locked in any pos- 15Wition. For ceiling, wall, shelf I For reflectedor bench fixing. illumination

25W

No.4 II

For wall or bench use. The 8x 10 ins.I di~user

25W or 40Wframe holding the safelightscreen can be swung upwardsto reveal an illuminated glasspanel for negative examination. ,The safelight panel is indirectlylit.

i ,.•No.7For ceiling suspension. Two pper: 0 15W or 25Wsafelights, an upper and alower, 10 X 12 ins. diffuserprovide reflected and direct Lower: Withillumination at the same time. 8 X 10 ins. diffuser

No.8For wall mounting. May be 8 X 10 ins. With 25W or 40Wfixed with safelight screen hori- diffuserzontal or inclined. The safe-light panel is indirectly lit.

Junior IA smaller version of the 10. 8 5 X 7 ins. I With 15W or 25WDarkroom Lamp. diffuser

SECTION SIX

Processing

GENERALIlford Limited supply chemicals and apparatus for most photographicprocessing operations. Ilford Chemicals include a range of packeddevelopers and fixing salts, as well as the individual chemicals for makingup these solutions. Ilford Apparatus is described in Section Eight-Photographic Apparatus.

The book" Ilford Formulae" contains' formulae for all photographicoperations together with useful advice on processing.

DEVELOPMENTThe Ilford Developers normally recommended for plates, films andpapers are as follows :-Pfates and Films

For general use ID-2 (metol-hydroquinone)For greater contrast ID-2 at 3 X normal strengthFor maximum contrast ID-13 (hydroquinone-caustic)

Bromide, Multigrade and Plastika PapersID-20 (metol-hydroquinone)

Contact PaperID-36 (metol-hydroquinone)

These are general recommendations; for the developers and developmenttimes recommended for individual materials, including special materialsnot listed above, see the instructions issued with the material, or thebook "Ilford Formulae. "

Development time and temperatureFor photographic processing it is best to work at a temperature in theregion of 65° to 70°F. (18° to 21° C.), and published development timesare therefore usually related either to 65°F. (18°e.) or 68°F. (20°C,},

Where conditions are such that working at these temperatures is notpossible, the development time required for another temperature maybe ascertained approximately by taking the recommended developmenttime and multiplying this by the appropriate factor given below. These


factors are applicable to M.Q. carbonate and M.Q. borax developers ofnormal composition, and correspond to a factor of 1.75 for every 10° F.(5tOC). They may need to be modified when using other developers.Development times knoum at 65°F. (18° C.)

55° F. 60° F. 65° F.(13°C) (16°C) (18° C)

x7/4 X 4/3 xl

Development time knollm at 68°P. (20° C.)60° F. 68° F. 75° F.

(16°C) (20°C) (24°C)Factor X 3/'2 X 1 X 2/3

Packed developersThe following Ilford Developers are available as packed chemicals invarious sizes: unless otherwise stated they are supplied in powder form.

ID-2 Metol-hydroquinone Developer, for plates and films.ID-5 Professional M.Q. Developer, for plates and films.ID-6 Pyro M.Q. Tank Developer-for roll films. Supplied with

replenisher.Fine Grain Developer (M.Q. borax).X-ray Developer (M.Q.).Replenisher for the above developer.M.Q. Developer, for Bromide, Plastika and Multigrade

Papers.Oscillograph Developer.M.Q. Developer, for Contact Paper.Blue Label X-ray Developer.Replenisher for the above developer.X-press Plate Developer. A rapid one-solution M.Q.

developer in concentrated liquid form for press work.Long-life M.Q. Developer, for trade house processing;

supplied with replenisher.Rapid Radiographic X-ray Developer, for use in the

operating theatre.Extra Fine Grain Developer.A developer containing paraformaldehyde for Litho-neg

Plates and Films.Concentrated universal developer for plates and films.

Contains no metol. In liquid form.M.Q. developer for use with all types of document papers

and machines.

Factor

ID-l1ID-19ID-19RID-20

ID-33ID-36ID-42ID-42RID-43

ID-46

ID-47

ID-48ID-50

Certinal

DocumentPaperDeveloper

70° F.(21° C)

x3j4

76° F.(24° C)

X 4/7

Fine grain developmentTwo Ilford fine grain developers are packed, namely:-'

ID-l1 Fine Grain DeveloperID-48 Extra Fine Grain Developer.

PROCESSING

ID-ll is an M.Q. borax developer which works rather slowly and givesmaximum shadow detail. Provided negatives are correctly exposed, thegrain given by this developer is fi~e en.ough for m~st work. ..

ID-48 is a developer intended primarily for use with 35 mm. rrunraturefilms. It is capable of giving finer grain than ID-l1 but causes someloss of speed. Negatives intended for processing in ID-48 should begiven an increase of 50 per cent. in exposure.Note.-Graininess is considerably affected by exposure. When finenessof grain is important, care must be taken to avoid Qver-exposure.

FIXATION

Use of an acid fixing bath, or acid stop bath before fixing, is recom-mended. Rinsing between development and fixation slows downdevelopment by carrying away the developer on the surface of thematerial, but some developer is inevitably carried over in the emulsionlayer into the fixing bath. An ~eid fixing bath quickly neutralizes suchdeveloper and so prevents staining. An acid fixing bath IS also helpfulin removing certain types of anti-halation backing.

Materials should, in general, be fixed for twice the ti:lle that they take toclear. This rule results in fixing times of the order of five rruns. In a freshacid fixing bath, though many high contrast materials ~an be fixed muchmore rapidly. Agitation is vital in early stages of fixation to ensure thatdevelopment is -stopped quickly and uniformly:

The following fixers are packed by Ilford LImited :-IF-2 Acid Hypo, for plates, films and papers. .Ilford Document Paper Fixing Salts. Acid hypo for use with all types ofdocument papers and machines.

Hardening-fixing bathsUse of a hardening-fixing bath or hardening stop b.ath betwe.en develop-ment and fixation is recommended both because it results in negativeswhich are better able to withstand abrasion, and also because negativeswhich have been hardened before washing absorb less water andtherefore dry more rapidly.

The following Ilford products are available for hardening :-IF-9, X-ray Chrome Alum Quick-Fixing Salts.llford Liquid Hardener. For addition to the fixing bath.llford Tropical Hardener. For use as a preliminary bath prior to develop-mcnt (see page 57).

RAPID DRYING

ILlpid drying by heat is not recommended except in properly designedell ing cabinets: even if the films have been hardened, drying by heatinvolves risk. Drying is helped by maintaining a good circulation of,1".111 air at a fairly low humidity. Admittedly the au must sometimesI•• warm d to achieve low humidity but the amount of heat needed IS

53


small. Avoid placing negatives too close together. Plates and films onnitrate base (e.g. roll films) may be quickly dried by immersion for twoor three minutes in methylated spirit (not stronger than 80 per cent.,at any rate for the final treatment) which should be used in amplequantity and frequently renewed; as it takes up water from each negative.The negatives will then dry within a few minutes in a brisk current of~L •

If spirit drying is used for films coated on safety, cellulose acetate, base(this includes miniature films and most flat films), special care must beexercised. The film must be passed through the bath quickly and notallowed to soak even for a few seconds.

WETTING AGENTS

Wetting agents are substances which cause water to flow more readily,and are therefore helpful whenever water has to wet a dry photographiclayer or has to be drained from a wet layer. An Ilford Wetting Agent ispacked for photographic use, in concentrated liquid form.

Processes in which wetting agents can be used with advantage includethe following :-

DevelopmentAddition of wetting agent to the developer promotes even flowing ofthe solution over the emulsion surface, preventing the formation ofairbells and washing off dust.Final wash waterIt is probably in the drying of plates and films that wetting agents havetheir greatest application in photography. If a few drops of wettingagent are added to the final wash water and the plates or films immersedin this for one or two minutes, they can be placed to dry without wiping.The surplus water will drain off readily and the front and back surfacesof the material will dry rapidly and be free from drying marks.Spotting and blocking-out negatives and printsUse of a little wetting agent in the water used with opaques, spottingdyes, water-colour pigments, etc., causes them to spread much moreevenly, giving a smoother and more satisfactory finish. This is veryuseful when blocking out large areas of a negative.Tinting of printsAddition of wetting agent to water-colour pigments and tinting dyesmakes them take much more readily to the paper surface.Addition to other solutionsWetting agents can be added to other photographic processing solutionsand will cause even action over the whole surface. This can be ofespecial value when negatives have been dried and handled and thenrequire further treatment.

PROCESSING 55

DESENSITIZING

Use of a desensitizer enables fast panchromatic materials-which wouldnormally have to be developed in complete d~rkness-to. be developedin weak light, enabling the operator to exercise control In processIng.Desensitizers are normally used in a preliminary bath prior to develop-ment, but in certain circumstances they may be added to the developingsolution.

The following desensitizers are manufactured by Ilford Limited :-

Desensitizing YellowLeaves no stain, and can therefore be used with colour filrr, e g., Dufay-color and other home-processed colour films. Gives little or no chemicalfog, and is a little more effective than Des~nsitizing Green with pan-chromatic materials. For use only as a preliminary bath: cannot be usedin the developer.

Desensitizing GreenA desensitizer' of wide application. Can be used as a preliminary b~thand is also suitable for use in some developers: see leaflet suppliedwith the desensitizer. Economical in use.

Both these desensitizers cause some speed loss which may be excessiveif bathing time is prolonged beyond the recommended time.Note.-Desensitizers may be applied to unexposed materials to reducetheir speed to light without affecting their speed to the direc~ action ofelectrons. This fact, however, cannot be applied to electron micrographybecause desensitizers lose their power in vacuum or, indeed, in absenceof oxygen.

PROCESSING UNDER TROPICALCONDITIONS

It is sometimes necessary to work at temperatures higher than the recom-mended one of 65°F. or 68°F. The development time must then besuitably modified. Rate of development increases rapidly with increasingtemperature and the rate of change differs with different developing.lgents. For a large number ofM.Q. carbonate and MiQ. borax developers,however a workable development time can be arrived at by dividingthe recommended development time by a factor of 1.75 for every 10° F.nse in temperature (see page 52). .

Most recognised developers will give satisfactory results WIth Ilfordmaterials if the time of development is suitably adjusted for the temper-utur in this way. In no case should development be prolon~ed beyondIIll' minimum required to give adequate contrast. At very high temper-.lllln,:sthe time of development may be inconveniently short, but can .beincreased by the addition of sodium sulphate and potassium brom:deIII tile developer. Sodium sulphate also has the advantage of reducing111 degree of swelling of the emulsion and potassium bromide reducesIhl' Co level which may otherwise be excessively high. This method is


recommended in preference to the alternative of diluting the developerwith water. Practical details for the method are given below.

Problems encountered at high temperaturesHigh working temperatures are normally to be avoided because ofseveral troubles which arise and because of the need for special processingtechniques if these are to be overcome. The main difficulties are causedby:-

(a) fog, which may rise to an objectionable level,(b) softening and undue swelling of the gelatin of the emulsion and/ or

backing, resulting in reticulation of the gelatin or actual melting.Softening may also lead to mechanical damage to the image, andhigh swelling means high water absorption leading to excessivedrying time.

RemediesBy taking proper precautions these difficulties can, however, be mainlyovercome.

(a) Fog can be kept in check by the addition of extra bromide to thedeveloper; this also helps to prevent development time frombecoming inconveniently short.

(b) Many materials are now hardened in manufacture to lessen thedanger due to softening of the emulsion, and this hardening alsorestricts swelling. Hardeners can also be applied by the user withsimilar benefits, as described below.

(c) Reticulation of the emulsion and backing layers and the tendencyof the emulsion to strip from the base is aggravated by differencesbetween the temperatures of the various processing solutions andwashing water. For instance, it would be unwise to use a developerapproaching 80° F., and a fixing bath which had been freshlymade up with cold water. All solutions and washing water should.therefore be as nearly as possible at the same temperature: differ-ences in temperature between these are more liable to cause frilling,blisters and reticulation than is a uniformly high temperature.

Recommended development techniquesTo overcome the difficulties referred to above the following techniquesare recommended for the development of plates and films:Up to 75° F.Follow normal processing methods but use a hardening-fixing bath-IF-9 chrome alum, or IF-15 potassium alum.75° F. to 85° F.Add 3 oz. sodium sulphate, Glauber's Salt to every 20 oz. workingstrength developer. This does not harden the gelatin but greatly reducesswelling in the developer. Slightly longer exposure and developmenttimes will be needed but there will be no other adverse effect on develop-ment. After development the material should be quickly rinsed in water

PROCESSING

or preferably immersed for 3 minutes in a 2t per cent. chrome alumsolution, care being taken to give vigorous agitation during the firstminute's immersion. It should then be fixed for at least 10 minutes inan acid hardening-fixing bath such as IF-15 (potassium alum) or, ifa chrome alum bath has been used, in an acid fixing bath such as IF-2,constant agitation being given for the first minute. The use of twofixing baths, the second being relatively fresh, is recommended.Over 85° F.Harden the material before development by use of one of the followingpreliminary baths :-

(a) Ilford Tropical Hardener.This is available in concentrated liquid form in various sizes, andshould be made up as directed.

or(b) A solution made up as follows :-

Sodium sulphate (Glauber's Salt) 4 oz. 1100g.Formaldehyde, 40 % solution t oz. or 12·5 c.c.Water, up to 20 oz. I 1500c.c.

Immerse the material in either bath for 3 mins., and follow by a thoroughrinse, after which processing may be carried out as in temperate con-ditions with the usual developer and fixing bath. These pre-hardeningbaths may, if diluted, also be used at temperatures below 8:'° F. IlfordTropical Hardener, bath (a), is more effective than bath (b).Control of fog .If fog is excessive at any of the above temperatures, potassium bromideshould be added to the developer. The bromide content may be increasedto double the quantity recommended for 68° F. (20° C.), or, with adeveloper containing metol, to several times if the temperature is veryhigh. This addition of bromide will also lengthen the required develop-ment time.

Washing and dryingAfter fixation, the plates or films should be washed for the minimumI ime consistent with adequate removal of hypo at high temperatures.Adequate washing may be obtained in 10 to 15 rnins. in running water,1)1" with about five changes of 2 mins. each. \X1ashing removes the fixing~:llts much more quickly when the temperature of the water is high thanwhen it is low.

Drying should be conducted as rapidly as possible, preferably in a1\11 r .nt of air.

UL TRA-RAPID PROCESSINGIII rc cnt years there has been an increasing interest in photographicIII Ihods, such as the recording of cathode ray tube traces, which demand1""1 the image be viewed within a few seconds of exposing the material.l'lus requires means by which the film can be processed extremely',,\ll1l1y.

57

58 PHOTOGRAPHY AS A AID TO SCIE TIFIC \'{fORK

Considerable work on this subject has been carried out in the IlfordResearch Laboratories. Some of the findings have been summarised inin the following paper :-

A. R. Burkin, " Ultra-rapid Processing of Photographic Materials,"Photo ]., 87B, 108-111, 1947.

This describes processing methods by the use of which pre-hardenedfilms can be completely processed in 6 to 15 seconds, and any film inabout 30 seconds. Detailed procedures and solution formulae are givenfor use with certain films.

Ilford Limited will be glad to advise on specific ultra-rapid processingproblems.

HYPERSENSITIZING AND LATENT-IMAGEINTENSIFICA TION

The terms "hypersensitizing" and "latent-image intensification"(latensification) include a number of pJ;.ocessesfor obtaining increasedspeed from a photographic material. Extravagant claims of increasedspeed by these methods are put forward at intervals, As a rule, a speedincrease of two to three times is all that can be expected, and that issubject to the type of emulsion and the duration of the exposure.

The following notes on practical methods have been extracted from thepaper :-

G. S. Moore, " The Last Ounce of Speed," Phot.]., 88A, 239-243, November, 1948.This paper contains a list of references on the subject.

Hypersensitizing (treatment before camera exposure)

(0) By meTCJlryvapourIt is difficult by this method to obtain reproducibility of results and toensure obtaining the optimum speed increase without running intoexcessive fog. Freedom of access of the mercury vapour greatly affectsthe required time of treatment. The process is more effective for longtime camera exposures than for short.

{b) By lightWhen the camera exposure is of long duration such as in astronomicalwork a short pre-fogging exposure of the order of 1/25th sec. should be:given, to an intensity of light sufficient to give just perceptible increasein fog with normal processing conditions. The amount of speed increaseobtainable depends on the characteristics of the emulsion and on thel.ength of time of the camera exposure-the only disadvantage of themethod being a slight decrease in contrast.

This method of hypersensitizing is of little or no value for increasingthe effective speed when the camera exposure is of short duration, of theorder of a fraction of a second.

PROCESSI G 59

Latensification (treatment between camera exposure and develop-ment)

(a) BY BATHING

Sulphur dioxide. Latensification by this process is carried out by bathingin a solution of sodium sulphite and potassium metabisulphite. Therelative quantities must be modified according to the type of emulsion.A twofold increase in speed was obtained by bathing Ilford HP3 filmin an aqueous solution of 3.4 per cent. sodium sulphite 0.5 per cent.potassium metabisulphite, and developing it for 3t minutes with vigorousagitation in dish strength ID-2 developer at 68° F. This process issuitable for instantaneous exposures when the negative is developedto a low gamma (0.6-0.8) to avoid excessive contrast and grain. Theincrease of speed over normal becomes smaller with increased develop-ment time.

Acetic acid and formic acid in organic solvents. Methods for intensifyingthe latent image by bathing in weak solutions of formic and aceticacids in organic solvents such as benzine, carbon tetrachloride or alcohol,containing not more than 1 per cent. of water, have been described in theliterature, but these techniques are unsuitable for general use owing tothe highly inflammable or toxic nature of the solutions employed.

(b) BY VAPOURS

Sulphur dioxide, mercury vapour, and the fumes of formic and aceticacids have been shown to give increased speed by intensifying the latentImage.

Sulphur dioxide. With I1ford HP3 and FP3 films, an effective speedincrease of two to three times may be obtained when the film is developedfor a normal time in ID-ll, for camera exposures of the order of 1/25 sec.or less.

A simple method of producing sulphur dioxide is as follows :-Take 1 oz. of a 10 per cent. solution of anhydrous sodium sulphite,and add to this 1 oz. of a 10 per cent. acetic acid solution. Put this in asmall dish. In order that the vapour may have free access to the film,it is best to load the film in the spiral film holder of a developing tank.Place both the dish and the film in an airtight tin, such as a large biscuitt in, and allow to fumigate for 24 hours.

Mercury. Mercury latensification appears to be more effective thanhyper-sensitization before exposure, but the difficulty of reproducibilityr {erred to above still arises. Useful when the camera exposure is of·.hort duration.

Acetic acid andformic acid. As in the case of bathing in solutions of these.u ids the process is not suitable for general use owing to the unpleasantIIIIt L1re of the fumes.

(c) BY LIGHT

~ hen the camera exposure time is of short duration, of the order of1/25th sec. or less, the' effective speed of many negative materials mayI>r increased two to three times by giving a long time uniform fogging


exposure to a weak light after the camera exposure. With emulsionstested, the hypersensitizing effect appears to be independent of the colourof the fogging light.

All that is necessary to obtain the maximum speed increase is to arrangethat the intensity of the fogging light is such as to give about double thenormal foz level with a fogging time of about 30 mins. to 1 hour.Fogging is

bmost conveniently carried out DY means of a safelight placed

about 6 ft. from the material, the safelight screen being masked down, jfnecessary, to obtain the required small fog increase.

As in other processes, the amount of speed increase depends on the degreeof development. Increasing the degree of development, either by in-creasinz the time of development or by using a more active developer,results bin a smaller speed increase. Latensification by light has theadvantage that it is possible to obtain high speed without excessivecontrast or graininess and it is simple and reproducible when once therequired conditions have been determined.

Hypersensitizing for the extreme ultra-violetThe gelatin of photographic emulsions absorbs extreme ul~ra-violetradiation, so that little or no image is recorded on a plate subjected tosuch radiation. If, however, the plate is made'to fluoresce under theaction of ultra-violet rays the visible fluorescence will cause an image tobe produced.

. To achieve this, bathe the plate in a 1per cent. solution of a good qualitymedicinal paraffin in pure ether, and dry the plate in a rapid current ofair. It is not necessary to remove the thin layer of paraffin before pro-cessing; it is so thin that it does not interfere with the normal mani-pulation of the plate.

Caution.-Ether is highly inflammable.

SECTION SE VEN

Filters and wedges

The manufacture of colour filters, neutral filters and neutral wedges ofall types has been carried out in the Filter Departmant of Ilford Limitedfor many years. The range of filters now available caters for everyphotographic need. Besides meeting the requirements of general photo-graphy, filters and wedges are supplied for use both in photographicand non-photographic branches of scientific work, including :-

photomicrography,photometry,absorptiometric and colorimetric analysis,spectrography.

The filters and wedges generally available are described briefly below.Full descriptions of these products, including transmission data andabsorption curves for each filter, are given in the book" Ilford ColourFilters," and brief descriptions of many of the filters in the booklet," Ilford Colour Filters, Wedges and Safelights."

In addition to the standard filters, special filters can be made to meetparticular needs, whether photographic or not.

COLOUR FILTERS

Over 70 different standard filters are made, most of which can be suppliedboth in the form of gelatin sheet and cemented between glass, threequalities of which are available. A few filters are supplied only in theForm of coloured glass. Filters of particular application in scientificwork include the following :-Q Filter (No. 805). A colourless filter absorbing ultra-violet radiationhut transmitting freely the whole of the visible spectrum and nearInfra-red.Chance OX. 1 U.V. Glass (No. 828). A very deep violet, almost black,Idler, transmitting ultra-violet radiation and for use in fluoroscopy.Supplied as glass squares and circles 3 mm. thick, one quality only.Dilute Complementary Filters. These are a series of pale filters of theI omplernentary colours: yellow (blue absorbing), magenta (green.ihsorbing) and cyan (red-absorbing). They are made in various strengths


indicated by a number after the initials BA, GA and RA (standing forblue-absorbing, etc.).

e.g., BA 0.3, GA 1.2The standard values range from 0.1 upwards in increments of 0.1.

The filters are so made that when three different filters wi h the samenumber are superimposed, a neutral is obtained, the density of the neutralbeing equal to the number.

These filters are useful in experimental work when a correcting filter,assessable only by trial and error, is required.Micro Filters Nos. 1 to 9 (Nos. 305, 303, 404,110,202,501,502, 104 and108). This set of nine filters has been designed for the use of the micro-scopist, to give the selected regions of the spectrum often required inmicroscopy. The filters are frequently supplied cemented in glass circlesfor fitting in the cell of the microscope sub-stage condenser mounting.Narrower transmission bands than those given by individual filters canbe obtained by using combinations of two different filters.Photometric Filters (Nos. 829, 830 and 83.1)are three pale blue filters forconverting light of one colour temperature to light of another colourtemperature. No. 829, for example, converts light from a tungstenfilament source (2850° K) to light of a colour temperature of 3600° K.No. 810 corrects light from .a tungsten filament source to mean noonsunlight.

Spectrum Filters. A set of eight Standard Filters (Nos. 601 to 608) withtwo Supplementary Filters (No. 600 and 609) for isolating narrowbands of the spectrum. Useful in the visual estimation of the absorbingqualities of other filters and in general colorimetric work, but notintended for ordinary photographic work.

Bright Spectrum Filters (Nos. 621 to 626). These filters are considerablybrighter than the Standard Spectrum Filters, and have been designedfor use with non-amplifying photo-electric colorimeters. The IlfordBright Spectrum Filter Set comprises these six filters with the additionof Standard Spectrum Filters Nos. 607 and 608, making eight in all.Mercury Filters (Nos. 806, 807 and 808). A group of three filters, violet,green and yellow, usually employed in conjunction with Ilford Q FilterNo. 805, a colourless filter absorbing U.V., and No. 809, a very paleyellow filter, for isolating lines of the mercury spectrum.Tricolour Filters (Nos. 304,404 and 204). A set of standard blue, greenand red filters. Among their many uses is the preparation of three-colourseparation negatives from original subjects, artists' originals or colourprints.Narrow-cut Tricolour Filters (Nos. 306,408 and 205). Blue, green andred filters transmitting narrower bands than the standard tricolour filters.For the preparation of three-colour separation negatives from colour.transparencies,

FILTERS AND WEDGES 63

INFRA-RED LAMP FILTERS

For infra-red photography in daylight a filter is placed over the cameralens. Ilford Limited manufacture Filter No. 207 for this purpose. Asupplementary Filter No. 813 is available for absorbing the residualextreme red, if desired.

The same procedure can be followed in artificial light or, alternatively,filters can be used over the lamps, and Ilford Limited manufacture speciallamp filters for the purpose. Infra-red Filter No. 207, with or withoutNo. 813, is employed bound like a safelight screen, for placing over thelight source. This enables photographs to be taken in apparent darkness,the filament of the lamp being only just visible through the No. 207plus No. 813 combination. For scientific purposes an infra-red lampfilter can be provided through which even the filament is invisible.

NEUTRAL FILTERS

Two types are made.Non-scattering type. Grey filters of any degree of absorption can besupplied to order, either in the form of gelatin film or cemented betweenglass. These filters are not only free from perceptible colour, but arespectroscopically almost neutral between 4600A and 6400A. They arethus suitable for the control of illumination in optical instrumentsemploying visual observation. The absorbing medium of these filtersis colloidal carbon, corrected with a small amount of dye, giving aminimum of residual scatter.Silver type. Neutral filters can also be supplied in which instead of colloidalcarbon the absorbing material is silver in a state of division similar to thatin a photographic image. With these, scatter is considerable, and theiruse lies mainly in photographic investigations where it is desirable tosimulate the conditions obtaining with, say, a photographic negative.

NEUTRAJ.. WEDGE SCREENS

The materials used for neutral filters are also used for making continuousoptical wedges. Wedges are not normally kept in stock: the require-ments of individual users, both as to size and gradation, are so veryvariable that practically every wedge is made to order. Directions for( rdering are given in the book /, Ilford Colour Filters."

COLOUR WEDGE SCREENS

1\ number of Ilford Colour Filters ate available in the form of continuouswedges graded linearly from zero to a maximum, which may be thenormal full strength or a stipulated fraction thereof. These are high-,l'rade optical products, suitable for use in optical instruments, and havingll1anyuses in experimental work.

As an example, wedges in the three standard complementary colours,'('IIow, magenta and cyan, of suitable strength, combine to form an


excellent neutral, and, when adjusted, can produce any colour withintheir range, while in pairs they give wedges of the three primary colours,blue, green and red. This set of wedges could form the basis of a sub-tractive colorimeter.

ILFORD DENSITOMETER

This is a direct-reading instrument for measuring transmission densitiesof ordinary photographic negatives. Visual observation of the photo-metric fields is employed. Two models are available, one for batteryuse, the other for A.C. mains. The battery model works from a No. 800dry cell battery. The A.C. model is supplied with a transformer andworks from 200-250 V A.C. mains supply.

DENSITY MEASUREMENT WITH THE S.E.I.EXPOSURE PHOTOMETER

Special accessories enable the S.E.I. Exposure Photometer to be usedas an alternative to the Ilford Densitometer for the measurement oftransmission densities, and also for the measurement of reflectiondensities. These accessories comprise ;-

1. A supplementary lens attachment to enable the photometer to befocused on images close to the telescope.

2. An illuminator consisting of a box with opal window illuminatedby a 6V. lamp. The box contains a transformer for supplyingboth the illuminator and photometer lamps.

3. An external supply adaptor carrying a lamp similar to that in theilluminator. This replaces the lamp and battery in the photometerand enables it to be operated from the illuminator transformer.

A booklet describing the use of the photometer with these accessoriesis obtainable upon request.

SECTION EIGHT

Photographic apparatus

Attention is drawn to the many Ilford Accessories now available. Thefollowing list is not exhaustive but contains a large number of theaccessories likely to prove of service in scientific and industrial photo-graphy.

LightingLighting sets.Floodlights.Spotlights.Photoflood bulbs.

X-rayCassettesIntensifying screens.Processing hangers.Darkroom film containers.

P. Processing tanks and units.

rocessIng Wet film carriers.Darkroom clocks. Drying cabinets.Printing frames. Viewing lanterns.Thermometers. Dental film processing equipment.Developing tanks for plates, .

flat films and roll films. MIscellaneousDishes. Photo-electric exposure metersMeasures. . (see page 44).Immersion heaters. S.E.!. exposure photometerPlate draining racks. (see page 44).Cardiographic development outfits. S.E.I. photometer accessories forDarkroom lamps and safelights densitometry (see page 64).

(see pages 47 to 50). Camera stands and tripods.Densitometer (see page 64).Lantern slide storage

and transit boxes.Dry mounting presses.

PrintingPrinting frames.Reflex printing box

and accessories.Enlargers.

Details of any Ilford Accessory will be supplied on request.

SECTION NINE

Ilford publications

Copies of the following books and leaflets can be obtained on applicationto Ilford Limited. Unless otherwise stated they are free of charge.

MISCELLANEOUS

-f- Ilford Manual of PhotographyRecently revised, this book presents a simple and straightforwardaccount of modern photography from which a thorough workingknowledge of the subject may be obtained.Edited by James Mitchell, M.A., B.se., F.R.P.S.Nearly 500 pages, size 8tx5t ins., price 10s.

'f... Ilford Manual of Process WorkProvides full descriptions of all photo-engraving processes.Author: L. P. Clerc, HON. F.R.P.S.

440 pages, size 8t X 5t ins., price 15s.

-I-The Photographic Recording of Cathode Ray Tube TracesDeals concisely with theory, technique and equipment and includes acomprehensive bibliography.Author: R. J. Hercock, n.sc., A.R.Le., A.INST.P., F.R.P.S.

60 pages, size 8t X 5t ins., price 5s.. /

t- 35 mm. Filmstrip TechniqueA practical work by Peter Hansell, F.LB.P., F.R.P.S. Fully illustrated.82 pages, size 8t X 5t ins., price 7s. 6d.

Ilford Photographic Emulsions for Nuclear Research4 pages, size 8t X 5t ins.

.j. Ilford FormulaeContains formulae for all kinds of photographic processing, includingdeveloping, fixing, reduction, intensification, clearing and toning.48 pages, size 8t X 5t ins., price ls .

./

ILFORD PUBLICA 1'10 . S 67

-t Printing and EnlargingAn Ilford Textbook describing in " straightforward way the principlesof contact printing and enlarging. } At the back is a wallet containingspecimens of Ilford Paper surfaces.44 pages, size 8t X St ins., price 2s. 6d.Ilford Book of Winter Photography44 pages, size 8t X 5t ins., price 2s. 6d.

DOCUMENT COPYINGIlford Document Papers-Instructions for their use and application12 pages, size 8t X 5t ins.The Technique of Micro-copying12 pages, size 8t X 5t ins.Document Copying with the Ilford Reflex Printer4 pages, size 10X 8 ins.

COLOUR FILTERS-I- Ilford Colour Filters

A new edition giving complete technical information on all the standardIlford Colour Filters, Wedges and Safelights. Transmission values atdifferent wavelengths are tabulated and absorption curves are givenfor each filter.64 pages, size 8t X 5t ins., price 5s.

1- Ilford Colour Filters, Wedges and SafelightsA booklet describing the most widely used Ilford Filters, etc.12 pages, size 8t X 5t ins.

J. PanchromatismContains a simple explanation of colour rendering in monochrome,with illustrations showing the applications of panchromatic materialsand the various uses of Ilford Colour Filters.42 pages, size 9! X 7t ins., price 2s. 6d.

k Ilford Darkroom Lamps and Safelights4 pages, size 8t X 5t ins.

X-RAYPositioning in Radiography .A valuable aid for those practising radiography and for students prepanngfor examinations and diplomas.Author: K. C. Clark, M.B.E., HO .F.S.R.Over 500 pages, 1,400 photographs, fifth edition, price £4 Os. Od,Ilford X-ray Films and Screens for Industrial Radiography16 pages, size 8t X 5t ins.Ilford Intensifying Screens for Medical Radiography8 pages, size 8t X 5t ins.Ilford Catalogue of X-ray Materials and Accessories40 pages, size 8t xSt ins.

68 PHOTOGRAPHY AS A AID TO SCIE TIFle WORK

Dental Radiography with Ilford Dental X-ray Films4 pages, size 8t X 5t ins.Ilford X-ray Printing Service4 pages, size 8t X 5t ins.Selected Tables and Useful Information for X-ray Workers56 pages, size 4 X 2i ins.Mass Miniature Radiography of the Lungs2 pages, size 9i X 7t ins.X-ray Darkroom Practice32 pages, size 8t X 5t ins.

ACCESSORIES

Ilford Accessories for Amateur Photography16 pages, size 8t x 5t ins.Ilford Densitometer for Direct Readings of Transmission Densities8 pages, size 6 X 5 ins.Ilford Presents the S.E.I. Exposure Photometer4 pages, size 8t X 5t ins.S.E.I. Exposure PhotometerInstruction book.32 pages, size 8t X 5t ins.S.E.I. Photometer Accessories for DensitometryInstruction book12 pages, size 8t '''C 5t ins.Ilford Advocate 35 rnrn, CameraInstruction book.16 pages, size 6 X 4 ins.Introducing the Ilford Advocate 35 mm. Miniature Camera4 pages, size 6 X 4 ins.Ilford Craftsman Roll Film Camera20 pages, size 7t X 4i ins.Ilford Portable Enlarger10 pages, size 7t X 5 ins.Ilford Photo-electric Exposure Meter, Model CInstruction Book.8 pages, size 5 X 4 ins.

CINE

Printed in England by Edson (Printers) Ltd., Watford.

Documents

Photography as an Aid to Scientific Work