edge effects

Definition: Local distortions of image density in film due to the movement of developer and developer products between regions of different exposure. * In an area of high exposure, developer is used up rapidly but in areas of low exposure, developer is comparatively active as there is little work to be done. This active developer migrates to area of high exposure and its activity causes a slight local increase in density. In areas of low exposure, the opposite happens.
Effective family
There is quite a family of edge effects, all caused by the same basic mechanism and are seen typically in slow- to medium-speed films developed by high-energy developers used at very low concentrations. They may also be seen in colour films that use developer inhibitor release couplers. Some image processing techniques e.g. edge sharpening through digital filters cause analogous effects.

Related Terms: Mach bands

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