Langford’s Advanced Photography 7th Edition

5 LANGFORD’S ADVANCED PHOTOGRAPHY

viewing conditions. It has to be based on ‘average’ observers reporting on just acceptable levels
of grain pattern. The main factors influencing graininess are:

1. The granularity of the film you use.
2. Image content, i.e. whether your subject has a lot of fine detail that ‘hide’ the grain structure or uniform areas,

proportion of midtones and the optical sharpness of its image. A soft-focus or movement-blurred camera image
is more likely to display its grainy structure, as this emulsion pattern may be the only sharp detail you can see.
However, a sharp negative printed through a diffused or unfocused enlarging lens will lose its grain pattern
along with image detail (Figure 5.7).
3. Exposure and contrast. A black and white negative wholly under- or overexposed shows lower contrast and
needs higher contrast printing, which emphasizes its grain pattern. Overexposure additionally scatters light,
further reducing contrast so the prints made on high contrast paper end up with more graininess. Low-contrast
subject and lighting conditions result in flat images which again need high-contrast paper, emphasizing
graininess.
4. Degree of development – normal, held-back or pushed. Also, with monochrome silver emulsions, the
choice of developer type. Overdevelopment and the use of speed-enhancing developers both increase
graininess.
5. Chemical after-treatment of the film image. Most solutions which reduce or intensify image density also increase
graininess.
6. Enlarging. Obviously, degree of enlargement is important, but so is type of enlarger (diffuser or condenser light
source). Printing paper contrast and surface texture – glossy or textured – is a major factor, but not the paper
emulsion structure because this is very slow and fine grained and not itself enlarged.
7. The viewing distance and the brightness of lighting on the final result. Also the conditions of viewing – a
transparency surrounded by strong light on a viewing box shows less graininess than when masked off with dark
surround.

Figure 5.7 Left: normal photography on grainy reversal colour film. Centre: shot with a diffuser over the camera lens. Grain is still
apparent. Right: reversal print from the left-hand transparency, with the enlarger lens diffused. Grain is blurred and thus visually lost,
along with image detail.

Graininess is not always a thing to avoid. As long as it can be controlled you can use it
creatively. Grain simplifies images by destroying unimportant small detail, evokes atmosphere
and breaks up large monotonous areas of tone and colour. To maximize grain, shoot with a

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FILMS – TYPES AND TECHNICAL DATA 5

small-format camera and high-

resolution lens on fast film. Keep the

image small (for extra enlargement

later) and use flat subject lighting so

that you can step up development to

increase graininess without creating

excessive image contrast. For black

and white work push-process fast

film in a speed-enhancing developer,

or use E-6 first developer giving

about 5 min at 25°C. Silver image

Figure 5.8 Grain can visually contribute positively to the atmosphere of a negatives can be slightly
picture. This old promotional advertising shot for a brewery works through overexposed, then overdeveloped
what it suggests in terms of a Sunday morning at the ‘local’. By Dick Swayne. and reduced in Farmer’s Reducer
(page 174). You next enlarge with a

condenser type enlarger, preferably a point source, onto high-contrast glossy paper. As a less-

subtle but easier-to-handle alternative, print through a grained screen sandwiched with your

film in the enlarger. Screens can be bought or made by yourself, by underexposing coarse-

grain film to an image of an evenly lit plain surface (Figure 5.8).

Edge sharpness

Boundaries between areas of the image – light and dark – tend to be exaggerated when silver

halides are developed. Figure 5.9 shows how the higher density of a boundary becomes

greater and the lower one less along the edge of light and dark. This so-called adjacency or

‘edge effect’ is due to chemical changes during development. Active developer diffuses from the

low-density area where it is underused, boosting development along the adjacent high density

one. Meanwhile, the oxidation by-products – bromide and iodide – released in largest quantities

from the high-density side slow development on the low-density edge of the boundary. All this is

Subject of practical importance, since
exaggerated edges give a

stronger impression of image

Reproduction sharpness. This principle is
with edge being used in digital
effect sharpening filters available in

Density all image manipulation
Density
applications. High-acutance

black and white developers

Distance Distance are formulated to exaggerate

Figure 5.9 Adjacency effect. When a subject boundary between dark and light (left) is edge effects. They may
imaged onto film the density change in the processed negative does not show the however increase graininess
expected profile (solid line). Instead, chemical changes across the boundary give an by sharpening up edge
exaggerated edge effect. This improves visual sharpness. Right: the effect as recorded by contrast (Figure 5.10).
a micro-densitometer showing a trace across an actual film image.

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5 LANGFORD’S ADVANCED PHOTOGRAPHY

Figure 5.10 Left: unprocessed image. Right: image sharpness is increased digitally. The edge contrast is boosted but the result looks
grainier too. By Sophie Triantaphillidou.

Film MTF

In Chapter 3, we saw how the quality of lens performance can be shown by a graph which
plots image response (modulation) with respect to coarse and to fine detail (low-to-high
spatial frequency, measured in cycles/mm or lp/mm). Modulation transfer function (MTF)
is also published for films (see Figure 5.11). Notice how the graph shows 100% modulation

1000 200
Process E-6
100
Response (%) 100 B Response (%) 70 B
70 G 50 G
50 2 3 4 5 10 20 R 600 R 600
30 30
20 50 100 200 20 50 100 200

10 10
7 7
5 5
3
2 3 Exposure: Daylight
2 Process: E-6
1
1 Density: 1.0 Diffuse Visual
1

1 2 3 4 5 10 20

150 150

100 100
70 70
50 50

Response (%) 30 Response (%) 30

20 20
Exposure: Daylight Exposure: Daylight
Process: CN-16X Process: CN-16

10 10

7 7
5
5

33

22
1 5 10 20 50 100 200 1 5 10 20 50 100 200

Spatial frequency (cycles/mm) Spatial frequency (cycles/mm)

Figure 5.11 Top: MTF curves of Kodak Elite Chrome 100 (left) and 400 (right) colour slide films. The MTF curves published by Kodak
are for the three different colour records. In this case, the green MTF is the most important because the eye is more sensitive to the
yellow-green part of the spectrum. Reprinted with permission from Eastman Kodak Company. Bottom: MTF curves for Fujicolor 100 (left)
and 1600 (right) colour negative films. The slower ISO 100 film shows better response in middle and high frequencies and a higher cut-
off than the very fast ISO 1600 film. Reprinted with permission from Fujifilm UK Ltd.

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FILMS – TYPES AND TECHNICAL DATA 5

(or more, depending on the film and manufacturer) with coarse to medium detail, because edge
effects have greatest influence here and boost contrast. At the finest detail, shown at highest
frequencies at the end of the scale, grain size and light-scatter within the emulsion take their
toll, so that response dips. The point on the frequency axis where the graph line drops to 10%
response is sometimes quoted as the maximum resolving power of the film. Typical limits
are about 200 cycles/mm for very fine grain, slow black and white film, 120 cycles/mm for a
medium speed colour negative film and 80 cycles/mm for a medium-speed colour slide material.

Most manufacturers’ technical data sheets on films include an MTF graph for comparative
purposes. These prove that a fine-grain thinly coated, slow film have generally a higher curve
than a fast one. You can also take into account the MTF curve for the lens you are using,
‘cascading’ the two together by multiplying their fractional values (i.e. modulation values from 0
to 1) at each spatial frequency. The result shows the combined performance of your lens ϩ film,
as shown in Figure 5.12. Clearly, a low-resolution film can demolish the effective practical
performance of an expensive lens, just as a poor lens nullifies a high-resolution film. MTF
can be taken even further by considering the performance of enlarging lens and printing paper.

100

Modulation 50 ISO 125/22°
40

Lens ϩ film
30

20

10 100
0 1 5 10 20 30 40 50
Frequency (cycles/mm)

Figure 5.12 MTF curves of camera lens, film and combined MTF of the camera and film system.

100 As discussed in Chapter 3, you can also apply a

Contrast sensitivity 80 cut-off frequency beyond which performance is

(Viewing distance unimportant (say 40 cylces/mm). The exact figure will

60 250 mm) depend on camera format, degree of enlargement

40 and the distance expected for viewing final pictures

(Figure 5.13).
20

0 2 4 6 8 10

Frequency (cycles/mm) Characteristic curves

Figure 5.13 Typical contrast sensitivity function of Curves like Figure 5.14 are the oldest type
the human visual system (considered as the MTF of performance graphs for light-sensitive
the eye), for a typical reading distance. Multiply emulsions, pioneered by scientists Hurter and
figures on the frequency scale by seven to relate Driffield working in Britain in 1890. Traditionally
them to a 35 mm film frame which will be enlarged
to 8 ϫ 10 in. print.

known as ‘characteristic curves’, they are also called

H & D curves, density curves or D log H curves. The curve plots the resulting image densities,

measured after processing and plotted on the upright y-axis against a wide range of light

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5 LANGFORD’S ADVANCED PHOTOGRAPHY

Density 2.0 2.0 Density
1.0 1.0

123 4 1234
(a) Relative log exposure (b) Relative log exposure
B
4.0 G 4.0 Exposure: Daylight 1/50 sec
Exposure: Daylight R Process: E-6
Densitometry: Status M B Densitometry: Status A
Log H Ref: Ϫ1.44 G
3.0 R
3.0
Density Density 2.0
2.0

1.0
1.0

0.0 Ϫ3.0 Ϫ2.0 Ϫ1.0 0.0 1.0 0.0 2.0
Ϫ4.0 Ϫ4.0 Ϫ3.0 Ϫ2.0 Ϫ1.0 0.0 1.0
(c) Log exposure (lux-seconds) (d) Log exposure (lux-seconds)

Figure 5.14 Characteristic curves of (a) an ISO 100/21° black and white film, (b) an ISO 400/27° black and white film, (c) an ISO
400/27° colour negative film and an ISO 400/27° colour slide film. Diagrams (a) and (b) reprinted with permission from Ilford
Photo/Harman Technology Limited. Diagrams (c) and (d) reprinted with permission from Eastman Kodak Company.

exposures given to the film (log relative exposure), scaled on the x-axis of the graph. Both
density and log exposure are logarithmic quantities (density is the log of the film opacity).

As shown in Langford’s Basic Photography, a quick comparison of characteristic curves
for different films shows you many of their vital differences. Relative contrast can be seen from
the general slope of the curve; speeds can be compared broadly from how far to the left the
curve rises from horizontal. Exposure latitude can also be gauged. This is done by seeing how
far the range of exposure units representing your subject from the shadows to highlights
(1:100 brightness range ϭ 2.0 log E) can be moved in either direction along the log E axis before
they fall on the unacceptably tone-flattening toe or shoulder of the curve. Characteristic curves
published in sets like Figure 5.15 also show the effect of different degrees of development on
density and contrast.

Reversal materials have characteristic curves which slope downwards as light exposure
increases (see Figure 5.14 (d)). After reversal processing, parts of the image that contained most
light reproduce as having least density – a directly positive result. The slide or transparency must
have higher contrast to be viewed projected in total darkness as your final picture, unlike a
negative, which is an intermediate and contrast can be boosted in the print. It also needs good

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FILMS – TYPES AND TECHNICAL DATA 5

D-76 Density (D ) Processing: D -76, 20ЊC (68ЊF) clear highlights. These features
3.0 (Small tank development) are shown by a steeply angled
2.5 4170mmmiinnin...GGGϭϭϭ000...546335 curve and low density at the
2.0 bottom of the curve 0.2 (it is
1.5 mainly the density of the gelatine
1.0 film base itself) (Figure 5.16).
0.5
Characteristic curves of
colour film images are most often
prepared by exposing the material
to a transparent scale of grey

0 Ϫ3.0 Ϫ2.0 Ϫ1.0 Ϫ0.0 1.0 tones, the light, of course,
matching the colour temperature
Exposure [log H (lux-seconds)] for which the film is balanced. The
great majority of colour materials
Figure 5.15 Characteristic curves showing the effect of development time on recreate all the colours of the
the response of a black and white negative. The film is developed for 4, 7 and 10 picture through superimposed
min. Longer times result in higher densities and increased contrast (G is the
contrast index). Reprinted with permission from Fujifilm UK Ltd.

images in yellow, magenta and

cyan dyes. So after film processing

4.0 Normal processing every tone on the grey-scale image is checked out three
C Pushed two stops times with a densitometer, reading through a blue filter
to measure yellow dye density, then a green filter for
M magenta and a red one for the cyan layer density.
3.0 Y All three plots must coincide in shape along most of

Density their length, as in Figure 5.14 (c) and (d) graphs.

2.0 It is vital that the same filters and densitometer

colour response be adopted worldwide when

making comparative measurements of this kind.
1.0 Certified conditions known as Status A are used for

positive colour film images. Three slightly different

filter values are needed for evaluating colour negatives

0 1.0 2.0 3.0 because the dye images here are geared to best

Relative exposure (log E) suit the colour sensitivity of colour printing

Figure 5.16 Characteristic curves for 800/1600 paper, not your eyes. Conditions are then called
colour transparency film, given normal and (two Status M.
stops) pushed processing. Unlike negatives, extra
development lessens the final density of shadows. Looking at Figure 5.14 (c), you can see that
characteristic curves for a typical colour negative film,

read through correct blue, green and red filters, are

similar in contrast to regular monochrome negatives. They are also offset vertically. This

displacement is due to masking built into the dye layers, designed to compensate deficiencies in

negative and print dyes. Provided there is no displacement horizontally, and all curves match in

shape, colour printing will cancel out this apparent discrepancy. Programs for quality control

of colour processing make similar readings of test strips which are put through the system

at regular intervals to check any variations in solution chemical content, temperature, etc.

(see page 280).

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5 LANGFORD’S ADVANCED PHOTOGRAPHY

Spectral sensitivity

Afilm’s response to different colours of the spectrum is shown by a graph in which
sensitivity (usually ‘log relative sensitivity’, being the log sensitometric speed of the
photographic material determined at appropriate wavelengths) is shown against
wavelength. The main points to look for in spectral sensitivity curves for black and white
films are:

1. The highest wavelength cut-off point (Figure 5.17), showing whether a film is panchromatic, orthochromatic or
only blue sensitive. Ortho films finally reproduce red lips, red lettering, etc. as black or very dark, but films can be
handled under deep-red safe lighting. Blue-sensitive materials extend dark reproduction to greens but they are
safe under bright amber bromide paper lights.

2. The uniformity of response of panchromatic film. Most films are panchromatic, but some fast materials have
extended red light response which helps to boost speed and records more detail in deep-red subjects but also
tends to bleach lips and other pale reds. Colour film sensitivity curves are in sets of three for the blue-, green-
and red-sensitive layers. Each curve should just overlap so that every colour in the spectrum is recorded by some
response in one or more layers.

Ortho Pan

Sensitivity Blue Extended
sensitive pan

400 500 600 700
Wavelength (nm)

Figure 5.17 Spectral sensitivity curves for four types of black and white material. Extending panchromatic sensitivity to 720 nm boosts
speed, especially in tungsten lighting. But for general work the final, positive, reproduction of red from negative material of this kind may
be too bleached to be acceptable.

Colour balance

Colour films balanced for tungsten-lit subjects have blue-sensitive layers slightly faster in speed
than red ones (Figure 5.18). This compensates for the fact that tungsten-lamp illumination is
deficient in blue wavelengths relative to daylight. It has a lower ‘colour temperature’ (page 72).
Therefore, by adjusting emulsion sensitivities the manufacturers can make different films
balanced for practically any light source which gives out a continuous spectrum, i.e. contains a
mixture of all visible wavelengths. In practice, only a few colour balances are on offer because,
apart from daylight type, the market is quite small.

You may often have to pick the nearest film type and then make good any mismatch with a
suitable colour-compensating filter over the lens (see Appendix F). Even with colour negative
film it is still best to match up lighting and colour balance as closely as possible at the camera
stage rather than rely too much on filtering back during colour printing (Figure 5.19).

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FILMS – TYPES AND TECHNICAL DATA 5

G. sens. B. sens.
(Y forming)
B. sens. (M forming)
G. sens.
(Y forming) R. sens. (M forming) R. sens.

(C forming) (C forming)

Relative sensitivity
Relative sensitivity

400 500 600 700 400 500 600 700

Wavelength (nm) Wavelength (nm)

Figure 5.18 Colour-sensitivity curves for (left) daylight balanced, and (right) tungsten light balanced slide film. Only response above
the broken line is significant. Notice the extra blue sensitivity of tungsten light film. If exposed in daylight it needs an orange filter to
avoid excessive blue.

Film type Colour temperature Light source
3200 K Studio tungsten lamps
‘Tungsten’ or type B 3400 K Photolamps
Tungsten movie stock or
type A 5500 K Sunlight + skylight and most studio flash
‘Daylight’

Figure 5.19 The three main colour film types and their (unfiltered) compatibility with various white light sources.

Reciprocity failure

The reduction in film speed which occurs when you give a very long exposure to a very dim
image is usually presented as some form of table (Figure 5.21). Short-duration reciprocity
failure is less important. Modern films are designed to respond normally for very brief
(1/10 000 sec) bright images because this is needed for some forms of flash. However, long-
duration reciprocity failure means that you may have to extend exposures of 1 sec or beyond.
Remember this when using an AE camera in aperture-preferred mode which rarely takes
reciprocity failure into account. Make corrections with the camera’s exposure compensation dial.

With colour materials some form of pale correction filter may also be specified. Filter colour
varies with different brands and types of film. Reciprocity correction is most critical on
professional colour films, where sometimes separate types are made for different exposure times
(see Figure 5.22). Try to work strictly to manufacturers’ recommendations for critical record
work, studio portraits, etc. Fortunately, in a great deal of existing light photography – taken at
dusk or night, for example – slight colour variations are accepted as natural. Provided that you
remember to bracket your exposures towards longer times, complicated filtration and
multiplication calculations (leading to still more reciprocity failure) can usually be avoided.

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5 LANGFORD’S ADVANCED PHOTOGRAPHY

Kodak Professional T-max 100 Film Kodak Professional T-max 400 Film

Modulation transfer curves Modulation transfer curves

200 200

Response (%) 100 100 Response (%)
70 70
50 50

30 30
20 20

10 10
7
5 Exposure: Tungsten 7
3 Process: Small tank
Kodak Developer D-76, 68° F (20°C) 5 Exposure: Tungsten
2 Densitometry: Diffuse visual Process: Small tank

3 Kodak Developer D-76, 68° F (20°C)
2 Densitometry: Diffuse visual

1 1
1 2 3 4 5 10 20
50 100 200 600 1 2 3 4 5 10 20 50 100 200 600

Spatial frequency (cycles/mm) Spatial frequency (cycles/mm)

Spectral sensitivity curves* Spectral sensitivity curves*

2.0 2.0

0.3 greater than D-min 0.3 greater than D-min

1.0 1.0

Log sensitivity * 0.0 Log sensitivity* 1.0 greater than D-min
1.0 greater than D-min 0.0

Ϫ1.0 Effective exposure: 1.4 seconds Ϫ1.0
Process: Kodak Developer D-76,
Effective exposure: 1.4 seconds
68°F (20°C) Process: Kodak Developer D-76, 68°F (20°C)
Densitometry: Diffuse visual Densitometry: Diffuse visual

Ϫ2.0 Ϫ2.0
250 300 350 400 450 500 550 600 650 700 750 250 300 350 400 450 500 550 600 650 700 750

Wavelength (nm) Wavelength (nm)

*Sensitivity ϭ reciprocal of exposure (ergs/cm2) required *Sensitivity ϭ reciprocal of exposure (ergs/cm2) required
to produce specified density to produce specified density

Characteristic curves Characteristic curves

4.0 4.0
Exposure: Daylight
Process: Kodak professional Developer D-76; Exposure: Daylight
Small tank; 20°C (68°F) Process: Small tank
Densitometry: Diffuse visual
Kodak Developer D-76, 68°F (20°C)
3.0 Densitometry: Diffuse visual
10 min
7.5 min 3.0
6 min
12 min
108mminin
Density 2.0 Density 2.0

6 min

1.0 1.0

0.0 0.0

Ϫ4.0 Ϫ3.0 Ϫ2.0 Ϫ1.0 0.0 1.0 Ϫ4.0 Ϫ3.0 Ϫ2.0 Ϫ1.0 0.0

Log exposure (lux-seconds) Log exposure (lux-seconds)

Figure 5.20 Part of manufacturer’s data sheets for two black and white films, quantifying practical performance. Reprinted with

permission from Eastman Kodak Company.

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FILMS – TYPES AND TECHNICAL DATA 5

Indicated exposure time (sec) ᭤ 1 10 100

Most B&W neg films ϩ1/3 stop ϩ1/2 stop ϩ1 stops
Fujicolor 400 None ϩ2/3 stop Not recommended
Fujichrome 400 ϩ2/3 stop 5G Not recommended Not recommended
Ektachrome 64 ϩ1/3 stop CC05R Not recommended Not recommended
Ektachrome 400 ϩ1/3 stop ϩ1/2 stop Not recommended
CC05R CC10R Not recommended

Figure 5.21 Reciprocity failure varies with brand and film type. Filtration may be needed for color compensation.

Type S films

Exposure 1 1 1 1 1 1 1 1 1 1 1 Second
2 4 8 15 30 60 125 250 500 1000

Type L films

Figure 5.22 Type L professional colour films are formulated to be exposed at 1/30 sec or longer. Use Type S films for exposures of 1/15
sec or shorter. Type L films are also balanced for tungsten light 3200 K colour temperature, and Type S for daylight.

Product coding

Manufacturers mark up their products in various ways to identify type and batch.
Most sheet films have coded notches (Figure 5.23) to show type, and may have a
batch number impressed into the rebate of each sheet as well as printed on the
outside of the box. Notches have the advantage that in the dark you can ‘feel’ the type of film you

are loading. Rollfilm type information appears on the start and end of the backing paper and is

printed by light along the film rebate for you to read after processing. Most 35 mm cassette-

loaded film is DX coded to program the camera automatically for the film’s characteristics.

DX information is communicated through a panel of 12 squares on the outside of the

cassette, making up a chequerboard mixture of bright metal and

insulated (painted) patches. As shown in Figure 5.24, shiny patches

1 and 7 are always unpainted electrical contacts. Probes in the

camera film chamber use this common area as an earth. Battery

power applied through probes in other positions ‘read’

information according to whether they touch bare metal and

complete the circuit or are insulated by paint. Five patches

communicate the film’s ISO speed. Three more tell the camera film

length – to program its liquid-crystal display (LCD) ‘frames left’

counter and film rewind, for example. A further two patches

encode whether the film has narrow exposure latitude (colour slide

material) or wider latitude (colour negative), information used to

modify camera auto-exposure programs. These data are also useful

if the camera’s light-reading system works by comparing several

highlight and shadow ‘spot’ measurements (see page 163).

Modern 35 mm cameras have 10 probes in two rows to fully

Figure 5.23 Some notch codings from utilize all the DX-coded information. Cameras with less than six

top right corner of sheet films. probes default ISO 3200 film to 1600, while the simplest two-probe

101