Contrast and tonal range seem to be a part of photography that confuses
people most. Contrast is the difference of extremes - black and white,
dark and light. The greater the difference between them, the higher
the contrast. The numbers of shades of Gray in between (in black and
white) indicate tonal range. In colour the same is true with the complication
of colours and their associated properties. Working in black and white
we can produce a scale of specific tones between the black and white.
We cannot go beyond full black or white therefore all tones must be
contained between them.
Lighting also alters the tonal range in any scene we photograph.
However the number of recognisable tones can be altered during processing and printing. The appearance of the final print is not fixed; its apparent tonal range can be altered. To produce the best possible photographs control of the photographic process is essential.
Gray scale.
It is useful to photograph a gray scale to help check exposure and development.
Gray scales can be downloaded from John Paul Caponigro's http://www:johnpaulcaponigro.com excellent site or made in the darkroom on printing paper.
Some points to consider first are: -
1. The tonal range of daylight scenes often exceeds a films range. Some information is lost beyond the extremes of the film sensitivity. Further tonal range loss results when the print is made.
2. To obtain the fullest possible tonal range of a film or print careful consideration must be given to exposure and processing.
3. A full tonal range may not be the best way to print a photograph. The print should be sympathetic to the subject.
It is vital you standardise your methods to be able to control the final
print. Test using a readily available subject with a wide tonal range
or a well lit gray scale. Use the same film and developer. Keep notes
and results.
Since we are losing information in the form of tonal graduation it is important to choose the tones that we wish to use by correctly exposing for them. Bracket your exposures to get the best possible exposure-film is the cheap part of the process. Bracketing means giving exposures above and below the exposure calculated to be correct by the camera or you. A sequence may be +1, +1/2, indicated exposure -1/2, -1. Use the aperture to do this if possible (some cameras can do this automatically).
Bracketed exposures -negatives
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Poor highlight detail. Dense, high contrast |
Good contrast, fine detail. |
Low density, low contrast,Poor shadow detail. |
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The best exposure+development can be used to make the final print.
Which is the best negative? Harder, but in general you are looking for a negative that contains maximum information (detail) in the highlights and shadows without being over dense. Look for a negative that looks like the reverse of the prints you want. Make several prints from different negatives.
A "normal" negative should print at grade 2 or 2 ½ with a full range from black to near paper white (assuming you have a full range well-lit subject).
If the indicated exposure(from the exposure meter) is consistently too dark or light, printing at paper grades higher or lower than grade two you may adjust the exposure or development (not both). Increase or decrease exposure using the ISO setting(film speed) (or + or - setting 1/3 or ½ stop) or increase or decrease film development in small increments (easier if developing them yourself )(10-20%) and retest.
When you can consistently expose and develop negatives to print with a full range from one type of film and one type of developer then you can start too fine tune your development and exposure. Understanding of basic processes produces better final results. Similar methods can be applied for colour film and digital technology. Without some method results will tend to be hit and miss. Average subjects present little problem. Difficult subjects produce more interesting results but require better understanding of photographic technique.
This is only a basic idea of the process involved in fine tuning exposure/development. Various books exists on the zone system which can take this to perfection. However this too complicated for most people to fully apply especially in 35mm. An understanding of the zone system is none the less a good idea to help understand the process.
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