17Photographic Processing

Developers and Development

The purpose of development is to form a visible image corresponding to the invisible latent image. It continues the effect of light on the silver halide grain by converting exposed grains to black metallic silver (see Figure 1.1).

Exposed silver halide + reducing agent → metallic silver + oxidized reducing agent + halide ion

In this process of chemical development each crystal of the emulsion acts as a unit, it is either developable as a whole or is not developable. There is a second type of development in which the silver forming the developed image is derived from a soluble silver salt contained in the developing solution itself. This is called physical development but is not normally used ...

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