Film processing


When a photo is taken, a latent image is created on the film by the light passing through the lens. A decomposition of the silver halides (primarily silver bromide) suspended in the film’s gelatin layer occurs, and microscopic silver grains are created. However, to be made visible and stable, this latent image needs to be processed using a developer (e.g. phenidone or hydroquinone) and fixer (ammonium thiosulphate).

Developing black and white film

The exposed film needs to be placed in a development tank. This must be made in complete darkness, either in a darkroom or using a changing bag. The most challenging part is probably to put the film in the tank reel. Training in daylight with a discarded film can be recommended. A couple of measuring jugs, a measuring glass cylinder, a thermometer, and a stopwatch are useful.

The developing solution reduces the exposed silver halide crystals to black metallic silver. The exposed areas thereby become opaque (black or grey) and visible. A stop bath may be used to halt the process to avoid over-development. Unexposed areas are not affected and remain transparent.

The unexposed silver halides are then completely removed using a fixing bath. After this, the film is no longer light-sensitive. It is stable.

Thorough rinsing is required to remove all remaining chemicals from the film. Additionally, special additives may be incorporated to enhance rinsing and render the film anti-static, preventing it from attracting dust.

The developed film is negative, i.e. it needs to have white and black inverted. This can be achieved using an analogue enlarger that produces a positive paper enlargement, or a digital scanner.

Times, volumes, and temperatures

The details for the development process depends on the type of film and developer. This information is typically given on the film package, but it can also be found at Digitaltruth's Massive Dev Chart. The volumes of development and fixer solutions depend on the development tank. Some tanks have it printed on the tank. Otherwise, it has to be measured. Keeping the right temperature on the development solution is usually important. A thermometer is then essential

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