Fogging (photography)
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Fogging in photography is the deterioration in the quality of the image caused either by extraneous light or the effects of a processing chemical.
[edit] Light fogging
Light fogging can occur to the film in the camera because of a defect in the manufacture or use of the camera and is seen as dark areas in the negative which tend to occur over the full width of the film including the margins.
Light fogging on a print usually only occurs because of poor control of lighting in the darkroom and is seen as an overall dark veil across the print or, occasionally, as unintended solarisation.
[edit] Chemical fogging
Chemical fogging occurs at the processing stage when old or spent chemicals are used, chemicals are used in the wrong sequence, inadequate washing between processing stages or inappropriate chemicals are used. Because of the wide range of cause, the effects can be diverse ranging from coloured streaks and blotches through to the lack of an image or a totally black image. The most common cause is the use of old or spent chemistry which often results in a lack of contrast and an undesirable background colour - usually brown.
