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Tuatara: Volume 15, Issue 2, July 1967

Some Problems in Photographing New Zealand Forests. Part I

page 60

Some Problems in Photographing New Zealand Forests. Part I.


Despite All That has been Published on the various branches of photography, there appears to be little dealing with the subject as applied to either our own New Zealand forests or those of other countries.

In part one of this article, we shall deal first with the broader implications of the subject and, later, with some more specific examples.

‘Bush’ photography is less of a technique in itself than a variety of existing individual techniques to be applied as the occasion demands. It is an advantage to have had at least some experience in a number of fields. Architecture with its problems in light and shade, perspective and the frequent necessity for working within a confined space could well be one of these. At all events our ultimate aim should be to produce clear sparkling detail in every picture. It is not always possible to achieve such perfection, but with a little thought and consideration, we may at least avoid some of the major pitfalls. The best place to plan the making of a picture is at the very beginning. If our original camera position has been poorly chosen, no amount of technical skill is likely to improve a bad angle of view. Take time to study the scene from every viewpoint—perhaps a few feet to the left or right, higher up or lower down. Many a picture has been ruined by the careless masking of some vitally important feature. Small pieces of ‘bric-a-brac’ can assume the proportions of monsters in front of the lens. Even if some important feature is not completely blotted out this sort of thing can do nothing to enhance what little aesthetic value the picture might finally have.

The axiom that a scientific photograph should be a true and faithful representation of the original subject automatically excludes any form of deliberate faking, yet this is no reason to be content with something which is merely a dull and soulless record. ‘Sacrilege,’ cry the purists, ‘It is sinful for man to attempt to improve upon Nature.’ Whether this is true or not it is obvious that the process of tidying up could quickly get out of hand if taken to extremes. Good taste should play its part. It is a curious thing but in the clearing of rubbish and litter from the forest floor the situation is very page 61 quickly reached where it starts to look all ‘wrong’ anyway. At this stage the ecologist may well complain, but with so many of the modern cameras fitted with ‘brilliant’ type viewfinders, it should not be difficult to see exactly how much ‘tidying’ is really necessary.

Balance within a picture is important. Essential features should bear a harmonious relationship with one another. If there is one dominant feature, it should sit boldly within the boundaries of the four sides with all irrelevant detail either subdued or trimmed away, leaving no doubt as to what the photographer is trying to show.

A number of these problems can fairly be dealt with later on at the printing stage, but, as a parallel to an earlier remark it is best to pay attention to them from the very beginning.

The use of ‘Design and Composition’ in scientific photography must occasionally be limited, but they are as desirable in this field as in any other. To those unfamiliar with the terms ‘Design and Composition’ there could be a very real danger of implying a state of artificiality; yet if these are substituted by the word ‘Pattern’, the meaning immediately becomes clear. Pattern, in one form or another, is always present in nature—sometimes obvious, sometimes not.

Generally the mere repetition of a certain shape tends to produce its own harmony, so whether we like it or not, even the most ardent ‘copyists’ among us will have unwittingly, or perhaps unwillingly, reproduced the elements of design.

By imposing our own personality upon a scene we enable others to see that particular scene through our own eyes, but where scientific photography is concerned, this approach must be kept within bounds. On the other hand, if the photographer is not permitted to interpret nature, may he at least be permitted to assist her.

Innumerable books have already been written on the subject of design, and the student should have no difficulty in making a suitable choice.

Notes on Cameras

There is virtually no limit to the variety of cameras, films, equipment etc., for this type of work, but if we are interested in quality, nothing less than the best will do. It is for the individual to decide whether to use a large format camera, a medium format camera, or a 35 mm. Essentially he will have to choose between large negatives, medium sized negatives, or small, but one thing common to all three, most decidedly will be a good lens. It is useless contemplating serious work with a lens which is incapable of good resolution.

35 mm Cameras

To the average person concerned mainly with producing high quality photographs within a limited range, the 35 mm camera has page 62
Fig. 1: Pattern. Interior (close up). Toadstools. 4″ × 5″ llford H.P.3 cut film. Developed in I.D.l11. Printed on Agfa Portriga. Clear sky, but with sunlight heavily filtered through trees. White card positioned to reflect light into under side of subjects. Repetitive pattern.

Fig. 1: Pattern. Interior (close up). Toadstools. 4″ × 5″ llford H.P.3 cut film. Developed in I.D.l11. Printed on Agfa Portriga. Clear sky, but with sunlight heavily filtered through trees. White card positioned to reflect light into under side of subjects. Repetitive pattern.

page 63 much to recommend it. It is light and easy to carry, convenient for stowing in a pack and easily handled. Owing to its comparatively short focal length standard lens, reasonably good depth of focus is obtained with wide apertures which is a distinct advantage when working under poor lighting conditions. There is a far greater range of colour films for this size than for any other and, of course, it is very economical to run, especially when using the 36 exposure film as against 20. In the event of any uncertainty in exposure, it is comforting to be able to make a series of different exposures of a particular subject and choose the best. The increase in cost is kept to a minimum.

There will be a few in the 35 mm brigade who would probably have little use for any other than a standard 50 mm focal length lens, but the great majority will certainly require a shorter focal length of about 35 mm and at least one telephoto lens,* preferably about the 100 mm to 150 mm range. These days the popular one is 135 mm.

On the debit side, by far the greatest disadvantage of small cameras such as the 35 mm is the increased difficulty in maintaining quality especially in the larger sized prints, be they black and white or colour; although to be fair, we must concede that unsharp colour prints are slightly less distracting than are unsharp black and white. It is also inconvenient with any roll film (‘paper backed’ roll film in particular) to give each negative individual development and it is very frustrating to have to waste the greater part of a film for the sake of one or two exposures which may be required urgently. With 35 mm film it is possible to cut off lengths of film and develop them separately if necessary.

Medium Format Cameras (2¼″ × 2¼″, 2¾″ × 2¼″, 3¼″ × 2¼″)

Medium sized camera enthusiasts are today far better catered for than in the past. Over the last few years, as with 35 mm

* At this point a word concerning telephoto and long focus lenses might not be out of place. Confusion often arises as to what is meant by these two expressions. As a rule telephoto lenses are those in which the internal components have been constructed in such a way as to reduce their overall length, thus often making them considerably shorter, lighter and less bulky than their plain long focus counterpart. For this reason a telephoto lens is invariably used for long distance work even though a long focus lens gives a better overall image. A telephoto lens gives a good sharp image dead centre of the negative with progressive loss of quality towards the corners, whereas a long focus lens reproduces a flat field diagonally from corner to corner. The long focus lens is inconvenient in the field, but comes into its own in 35 mm macrophotography where we are dealing with image-subject proportions of around one to one, by enabling us to work at convenient distances from the subject. Those of us who have ever tried to illuminate a small specimen when using a standard lens on a 35 mm camera will appreciate the above remark.

page 64 cameras, many new names have emerged and most of the best are of Japanese origin — among then the Bronica (single lens reflex) and the Yashica (twin lens reflex). At one time the Rolleiflex and the Rolleicord virtually had the field to themselves but now the scene has changed and the choice is considerably wider.

The chief advantages of this size camera are the combination of relative lightness and compactness, coupled with the ability to produce a larger negative than the 35 mm. A further desirable feature found in the Hasselblad, the Bronica and recently the new single lens Rolleiflex is that all have detachable roll film magazines.

Large Format Cameras (4″ × 5″ upwards)

The larger format cameras are usually expensive to buy and expensive to run which puts them out of the strictly amateur range, but, as this article is intended for the more advanced worker as well, it will be in order to dwell on a few details concerning the Linhof Technika and such others as possess the same or similar camera movements.

The writer is fortunate indeed in that his Linhof and accessories are all provided for him and all that is expected of him is that he produce good pictures. The once popular 1/4 plate camera seems to have almost totally disappeared from the market leaving the 4″ × 5″ to take over. The two great drawbacks of the 4″ × 5″ are considerable increase in weight and running cost, both of which are more than offset by a vastly superior all round performance.

In this country large format cameras today are usually such well-known makes as the 4″ × 5″ Linhof Technika. A few of the older popular makes such as the ½ plate Thornton-Pickard will still be in use in some of the photographic studios as copying cameras, or even as enlarger bodies, but there is such a small number used in the field that for the purpose of this article they may safely be ignored. The Technika although a vast improvement on its predecessor the Field Camera, is basically rather slow and ponderous, but, for most bush work, that is no great disadvantage. It will need a good heavy tripod with legs that will sit firmly on the ground.

Another popular modern technical camera, is what is known as the ‘Monorail’ (e.g. Linhof Karden-Color). This is built on the principle of the optical bench. The whole camera unit is mounted on a single rail and although more versatile than the Linhof Technika, it is unfortunately suitable for only static subjects. Although it is ideal for many subjects, including bush work, it lacks the manoeuvreability of such makes as the Linhof Technika. Obviously, for the amateur, one would have to have an enormous amount of this kind of work to do to make the purchase of the page 65 Monorail worth while. It was this fact alone which decided the writer in favour of the Technika.

Notes on Black and White Films and Developers

The writer has at one time or another tried almost every trick in an attempt to reconcile high film speed with fine definition, with only limited success. We find ourselves in a position from which there appears to be no escape. Films are broadly divided into three main classes — slow, medium and fast. Those with the slowest speed have the finest grain and those with the fastest speed have the coarsest grain. So, on the one hand, we have the slow fine grain films giving the finest acutance (edge definition) but with considerable contrast, and, on the other, we have the fast films, with the coarse grain, giving us the speed and the reduced contrast we so much desire, but with an appreciable reduction in acutance. Vainly we search for a means to give us the necessary combination of speed, tone and detail. In desperation we turn to experimenting with developers. We read all the available literature on fine grain developers. We are impressed by all the advertisements proclaiming new and improved formulae for high speed, fine grain developers. We try them all and still the answer eludes us till, in the end, we appear to finish up exactly where we started. Sadder, but so much wiser, we come to understand that normal fine grain developers reduce grain and definition at the same time, and fine grain high speed developers do, in fact, increase the speed, but still leave a lot to be desired as regards fine grain. Many ultra fine grain developers offer little or no advantage with most types of high speed materials over ordinary fine grain developers with medium speed materials. Not only do most fine grain developers lower the effective emulsion speed of films but also most of them lower the effective speed of the faster films more than they do the slow. Something else which emerges from all this is that for average work too low contrast, in any sensitized materials is a disadvantage, but for our purposes it must be accepted as the only way to combat extreme contrast in the original scene.

It is next to impossible to offer definite advice as to what specific films or developer to use but the writer is currently using Agfa Record 4″ × 5″ with Rodinal 1-100 with surprisingly good results. Sooner or later one has to make up one's mind what combination to use and, in this instance, high speed film was chosen in conjunction with a soft working developer. Without too much stress on advertising, the comparatively high resolution which all Agfa films give, is a considerable help in offsetting the difficulties engendered by using a soft working developer.

One excellent way of overcoming excessive contrast is by selective printing, which means allowing for only the tonal range which is of page 66 interest to us, whether it be high, low or medium tones. This is comparatively simple to do: when assisted by selective shading and selective development with a swab of cottonwool soaked in warm developer on the thin poorly exposed areas of the print, the results should be even better.

Another good method of extending detail in the print is by the application of Farmer's Reducer on the clogged up highlights of the negative and very careful application of Farmer's Reducer to the darker shadows of the print. It should be noted that too strong or too prolonged use of this mixture will result in a discolouration of the print which is totally unacceptable. Fortunately, if a block is to be made of such a print, this discolouration will probably have little effect on the published image.

Water bath development of negatives and/or prints can be useful. This method allows the developer, in both cases, to build up the detail in less heavily exposed areas, while at the same time, suppressing the development of the more heavily exposed. Briefly, the negative or print is developed for a short period and then left without agitation in plain water so that the heavily exposed areas soon exhaust the developer with which they have become impregnated, while the action still continues in the lightly exposed areas. The plain water does nothing more than prevent uncontrolled ‘blotchiness’ in development. The one danger here is the risk of staining the negative, or, more disastrously, the print.

A more difficult technique, which could conceivably be used, is that of Tone Separation Negatives. As this is comparatively complicated, it does not lie within the scope of this article. In effect, it consists of making two negatives from the original negative to be printed in exact register and one after the other. One of these is intended for printing the highlights, and the other for the shadows, leaving the tones in between to sort things out for themselves. This they apparently do without over much difficulty.

A very popular technique, and slightly similar to the above, is that of masking. A weak soft positive transparency is made from the original negative and printed in accurate register with it. When enlarged together as a unit, one will tend to cancel out the other, thus having the desired effect of reducing the contrast.

A word of warning — the last two methods take quite an appreciable amount of care during registration, thus reducing their value for subjects containly much fussy detail.

Fill in Flash

Fill in flash has long been used as a simple and practical means of infusing quality in the shadows and is even better for colour than for black and white providing the area to be covered is not too large. In actual fact, when we come to cover really large areas, page 67 even multiple flash seems totally inadequate. On the other hand, unless we are deliberately reversing the situation over a small area we must remember to keep it purely as a fill in, and at no time must it appear to take charge. Once this happens, all feeling of sincerity is lost and we begin to be accused of faking. For publication the ideal light source ratio will be 4:1 for black and white and 2:1 for colour. Normal viewing of prints whether black and white or colour does however allow more.


All exposures must be as brief as possible, not only to arrest movement caused by the wind, but also to assist the acutance of the film. ‘Correct’ exposure is difficult to define but for our purpose it is based on the amount of detail just visible in the useful shadows and any greater exposure will achieve nothing more than to provide additional unwanted silver image directly affecting acutance. As with Agfa films, so it is with Agfa paper. Its ability to render detail is undisputable. One mitigating factor, which must not be overlooked is that if the final print does appear flat, we may rest assured that generally it will appear considerably sharper if and when it is reproduced for publication. This does not hold for newspaper work in which the coarse screen demands a print of considerable contrast. Under these conditions, the finer detail will not be reproduced anyway.

Forest Photography

For convenience the subject of ‘Bush Photography’ is divided into the following sub-headings:


General views of canopy.


General views of interior.


‘Close ups’ and semi ‘Close ups’ of individual features of interior.


A special case involving the use of a telephoto lens.

General Views of Canopy

The above heading implies a panorama over a wide area showing as much detail as possible of each individual tree in relation to its neighbour. One is not bound to use a certain type of camera for any particular aspect of bush photography, but in order to produce a print large enough to show sufficient detail it is an advantage to use a larger format camera. Other requirements will be a good high quality precision lens of normal focal length or wide angle.

As these photographs should be taken at infinity and in bright sunlight it will not be necessary to stop down too far to obtain depth of focus; therefore a comparatively slow film of medium page 68 contrast may be used. A tripod should be used wherever possible. Many photographers still do not appreciate the amount of shake in a hand held camera. It can be irksome carrying a large solid tripod in the bush, but results will always pay handsomely, especially where considerable enlargement is required from the negative. For black and white photographs there is no substitute for good bright clear sunshine at an angle of about 90° to the axis of the lens and in the morning for preference. (Usually morning light from about 9.00 a.m. till just before midday possesses a sparkling quality which is not present during the remainder of the day.) For colour, this general rule could be modified to include slight high white cloud. Colour films have much less latitude than have black and white and so anything that will compress the tonal range in this particular case without blurring the precious outline, will be an advantage.

For this type of work the writer has used to good effect Ilford FP3 and Ilford Pan F both developed in Ilford Hyfin. They provide a subtle balance between good full tonal range on the one hand, and clear cut definition on the other. The writer has also found that whereas all the Agfa films appear to have much higher resolution and give good definition they tend to fall short on tonal range. Similarly, slow or medium speed colour films are to be preferred to fast. So far, for 35 mm work Kodachrome II and Agfacolor transparencies (except for a tendency towards a slight brassiness in the latter) have proved superior, but it must be emphasised that for best results there still should be plenty of sunshine.

The use of filters is strongly recommended. For black and white occasional use of a U.V. might assist in cutting the distant haze, but for average work a × 2 yellow or a light green or mid green are sufficient. Orange or red should never be used at all where detail in foliage is required. Polarizing filters are slightly more tricky, and no really hard and fast rule can be laid down. On the one hand, while they may be useful in cutting haze, the elimination of specular reflections, mostly from leaves, is not always an advantage. Unfortunately, the latter effect, under certain lighting conditions, has a tendency to destroy the outline of the individual trees and we may find ourselves undoing a lot of the effect we have been striving to achieve.

At all times a colourless U.V. filter may be attached to or incorporated in a lens* and forgotten about, in the knowledge that even if it cannot do any good, it at least cannot do any harm. There are, however, also deeper and stronger U.V. filters which

* This does not take into account that, whereas earlier lenses were either ‘uncoated’ or ‘blue coated’, the more recent Japanese ones are ‘yellow coated’ thus often reducing the necessity for using U.V. filters at all.

page 69
Fig. 2: Canopy. 4″ × 5″ llford F.P.3 cut film. Developed in I.D.I 1. ×3 green filter. Printed on Agfa Portriga with considerable holding back in the shadow areas. Bright sun. Strong back lighting.

Fig. 2: Canopy. 4″ × 5″ llford F.P.3 cut film. Developed in I.D.I 1. ×3 green filter. Printed on Agfa Portriga with considerable holding back in the shadow areas. Bright sun. Strong back lighting.

should always be used with caution. Some, such as a Kodak-IA (pale pink). and Lifa C.R. 1.5 (light straw colour), are intended for use with standard colour films when the overall blue cast is excessive — such as at midday in summer with a clear blue sky, or in open shade under a clear blue sky, or even on a cloudy day with minimum sunshine. It should be borne in mined that film page 70 (particularly colour film) is inclined to register ultra violet light more readily than does the eye. Polarizing filters, under the right conditions, have the very desirable and practical effect, in colour films, of enriching the colour by the process of minimizing reflections. Again unfortunately, as in black and white, the latter effect may have a tendency to destroy the outline of the individual trees.

For black and white aerial work, at altitudes low enough to record any detail in the canopy, it is necessary to use a faster film such as Ilford H.P.3 or its equivalent* particularly if one wishes to use a green filter. This in turn will probably necessitate the use of a harder grade of paper in printing to obtain comparable contrast. For colour, on the other hand, by using a larger lens aperture (owing to faster shutter speed) on a 35 mm camera, it will be possible to just scrape by with Kodochrome II. A factor which must be considered with aerial work, as indeed with many other kinds of photography, is that when a lens is used at either its minimum or maximum aperture, performance falls off very considerably consequently in this case it is unwise to consider the use of an aperture greater than one stop below maximum.

In the manufacture of any lens, it is possible to have only one aperture of maximum efficiency. In a standard lens with a range of from f22 to f5.6 or f4.5 this would appear to be in the vicinity of f8 or f11.

General Views of Interior

We will probably find the heading ‘General Views of Interior’ comprises a greater variety of work than any of the other three and also a considerable amount of what applies to this group applies to at least two of the others.

Before attempting any discussion on any particular films at this stage it will be necessary to appreciate the lighting conditions most commonly encountered in the bush. Contrast will be the key word and all our efforts must be directed at compressing the tonal range without too much loss of sharpness in the final print. By using a soft film, soft developer and by printing on soft paper, it is not very difficult to make a print which will probably be very reminiscent of a soft, flat, fuzzy out-of-focus portrait.

Unfortunately, the situation demands a much more subtle approach than that. We aim to produce a high quality scientific photograph with full tonal range from near white to near black, with pinpoint definition throughout the critical areas. This is not so easily done.

Ideal lighting conditions could scarcely be more different from

* The writer has many times used Ilford F.P.3 film with Microphen developer in an attempt to increase the speed, but the final results have been less successful than when using H.P.3 with I.D.11.

page 71 those of the first group. Bright sunshine is definitely a disadvantage either for colour or black and white — in fact the more cloud, without being too heavily overcast, the better. Even under the latter conditions the wide range of tonal contrast is difficult to cope with but with bright sunshine it becomes impossible. Most films and transparencies are capable of rendering a tonal range of approximately 100:1, which is substantially below the maximum range found in nature. The transition from film to print leads to a further reduction in tonal range. Glossy bromide prints can only accommodate a range of approximately 60:1, and matt prints approximately 20:1.

Although most of us are aware how great a range of tone the eye can actually perceive, it still comes as a surprise how difficult it is to induce detail into the shadow and highlight portions of the final print. In fact, it is often a bitter disappointment especially as the original scene really did look so attractive in the viewfinder or on the ground glass screen. It is in this category that the problem of reducing contrast looms largest and it is often necessary to utilise many of the methods described under the heading ‘Notes on films and developers’.

Filters recommended in this group will be yellow or light green or mid green for black and white and pale pink or straw for such films as Kodochrome II (Daylight). Kodachrome X, with its faster speed, is designed for work under difficult conditions and although it requires less use of U.V. filters and generally less pampering for comparable results, it lacks good definition and produces a decided yellow veiling of the highlights. Kodachrome II should really not be used for exposures slower than ⅕ second without the assistance of compensating filters whereas, with Kodachrome X, it is possible to go to ½ second without compensating filters. Intelligent use of these filters could be regarded as taking one out of the amateur into the professional category. Most of us are aware that ultra violet light possesses a higher frequency than does any of the visible colours of the spectrum and so, on passing through cloud, the warmer colours tend to become filtered out, leaving the ultra violet to pass on virtually unchecked. As standard colour films are designed for use in balanced daylight, this is the very reason why any adjustment is necessary for their use in dull weather. One more factor which must be taken into account is that the light in the bush will have an overall tendency towards green. This will produce a corresponding colour cast in the film and will be fairly persistent no matter what colour film is used.

A whole series of CC filters are available primarily for the correction of colour casts in colour printing from colour negatives, and these filters are ideal for this purpose as well. The filters are available locally in 2 × 2in and 3 × 3in gelatine sheets and are page 72
Fig. 3: (Left). Interior (large area within forest). 4″ × 5″ Agfa Isopan Record cut film. Developed in Rodinal 1 - 100. X2 yellow filter. Printed on Agfa Portriga with considerable holding back in large shadow areas. Pronounced reduction on lower half of print. Heavily overcast sky. Negative exposed under ideal lighting conditions for this type of work.—cf. right-hand photograph. (Right). Interior (large area at forest edge). 4″ × 5″ Ilford H.P.3 cut film. Developed I.D.11. (overexposed and underdeveloped). Printed on Agfa Portriga with considerable holding back in large shadow areas and prolonged local printing in distance and middle distance. All larger shadow areas relieved with local reduction. Slight diffusion by high white cloud. Negative exposed under difficult lighting conditions resulting in contrast between heavy shadow in foreground and brilliant harsh lighting in distance. During the process of reduction of foreground shadows some local highlights have become bleached out. In order to prevent attention being distracted too much fom the main subject, it was found necessary to stipple these areas in again with the assistance of black photographic dye.

Fig. 3: (Left). Interior (large area within forest). 4″ × 5″ Agfa Isopan Record cut film. Developed in Rodinal 1 - 100. X2 yellow filter. Printed on Agfa Portriga with considerable holding back in large shadow areas. Pronounced reduction on lower half of print. Heavily overcast sky. Negative exposed under ideal lighting conditions for this type of work.—cf. right-hand photograph.
(Right). Interior (large area at forest edge). 4″ × 5″ Ilford H.P.3 cut film. Developed I.D.11. (overexposed and underdeveloped). Printed on Agfa Portriga with considerable holding back in large shadow areas and prolonged local printing in distance and middle distance. All larger shadow areas relieved with local reduction. Slight diffusion by high white cloud. Negative exposed under difficult lighting conditions resulting in contrast between heavy shadow in foreground and brilliant harsh lighting in distance. During the process of reduction of foreground shadows some local highlights have become bleached out. In order to prevent attention being distracted too much fom the main subject, it was found necessary to stipple these areas in again with the assistance of black photographic dye.

page 73 extremely cheap. The expensive form is of optical glass and is available on indent only. However, in photographing forest interiors irrespective of the density required to remove the colour cast Magenta is the only one which should concern us.

The following table contains a complete list of all the Kodak CC filters available with a corresponding exposure increase in stops.

Kodak Cc Filters — Exposure increase in stops
Yellow Magenta Cyan Red Green Blue
CC05Y _ CC05M ⅓ CC05C ⅓ CC05R ⅓ CC05G ⅓ CC05B ⅓
CC10Y ⅓ CC10M ⅓ CC10C ⅓ CC10R ⅓ CC10G ⅓ CC10B ⅓
CC20Y ⅓ CCC20M ⅓ CC20C ⅓ CC20R ⅓ CC20G ⅓ CC20B ⅔
CC30Y ⅓ CC30M ⅔ CC30C ⅔ CC30R ⅔ CC30G ⅔ CC30B ⅔
CC40Y ⅓ CC40M ⅔ CC40C ⅔ CC40R ⅔ CC40G ⅔ CC40B 1
CC50Y ⅔ CC50M ⅔ CC50C 1 CC50R 1 CC50G 1 CC50B 1 ⅓

In addition to removing colour casts CC filters may be used to counteract effects of storage, processing conditions and reciprocity failure.

All films (black and white and colour) are subject to the ‘Law of Reciprocity’ * failure when used with long exposure times. The

* Reciprocity Law

(Quote: The Focal Encyclopedia of Photography.)

Photographic exposure is the result of allowing light of a certain intensity to act on a sensitive emulsion for a specified time. According to the reciprocity law of photochemistry, so long as the exposure (light intensity × time) remains constant, the response of the emulsion is the same — i.e. if the intensity is doubled and the time halved, the blackening produced on development should be unaffected.

In practice photographic emulsions do not strictly follow this law. The maximum blackening is produced by exposure for a moderate time to a moderate intensity of light. Very low intensities of light with correspondingly long times or very high intensities with very short times produce less effect. The resulting reciprocity failure may show itself with the very short exposure of electronic flash or with very long exposures (e.g. in astronomical photography. In either case more than the calculated exposure (up to three times normal) may be required.

page 74 long exposure made necessary by low light intensity must be further increased to compensate for this ‘reciprocity failure’. The same applies to colour film but with an additional exposure increase appropriate for whichever CC filter is used. Photographic text books insist that these suggestions are to be taken as guides only and, for critical work, they should be checked by practical tests.
Reciprocity Failure and CC Table
Filter adjustment and exposure increase in stops
Film Exposure time (seconds)
1/10 1 10 100
Kodachrome II Daylight-type CCOSR + ⅓ CCIOR + ⅔ CC20R + 1 ⅓ CC25R + 2 ⅓
Kodachrome II Prof. Type A CC05R + ⅓ CC10R + ⅔ CC20R + 1 ⅓ CC25R + 2
Kodachrome-X Dayllight-type NF None CC05M + ⅓ CC05M + ⅔ CC10R + 1 ⅔
Ektachrome-X Daylight type NF None CC05Y + ⅔ CC20Y + 1 ⅓ CC40Y + 2 ⅔
Ektachrome Daylight (E-3) CC10B + ⅓ CC30B + 1 CC50B + 2 CC70B + 3 ½
Ektachrome Type B (E-3) NF None NF None CC05M + ½ CC10M + 1 ½
High Speed Ektachrome Daylight CC10B + ⅓ CC108 + 1 CC05G + 1 ⅔ CCOSM + 2 ⅔
High Speed Ektachrome Type B NF None CC05G + ⅔ CC10G + 1 ⅓ CC05Y + 2
Kodacolor-X NF None NF None NF + 1 NF + 2
NF = No Filter.
The exposure increase, given in lens stops, includes the adjustment required by any filters suggested.