Processing variations

The time and temperature technique of processing is comparatively modern. In the pre-panchromatic film era, when films could be developed in red safe lighting, development by inspection was a common practice. The photographer watched the image build up on the plate or film and learned by experience to judge the exact time to stop development. Often it was the point at which shadow detail could be seen through the back of the material as it lay in the developing dish. This technique offered an in built compensation for exposure error and for the subject contrast. Such techniques are impossible with modern films and in fact are largely unnecessary. The older films were a great deal slower and responded much more readily to exposure and development variations. They had considerably less exposure and development latitude, particularly exposure latitude. To some extent it is still possible to shorten exposure and prolong development to increase contrast or to increase exposure and shorten development time to lower contrast but the variations need to be rather drastic and the results can be unpredictable. Normal exposure can be accompanied by increased or reduced development time to vary image density, and might have a marginal effect on contrast. The technique has no particular validity in extremely low lighting, except as a desperate measure because no support for the camera is available to allow a longer shutter speed to be used. Its true value is in capturing action shots in dull light.