fog

Definition: (1) Non-image forming density in film that has effect of reducing shadow contrast. * Caused by (a) density of emulsion even when unexposed; or (b) stray, non-image forming light and other radiation due to light scatter or internal reflection in optical system or background e.g. cosmic radiation; or (c) unwanted chemical effects during processing e.g. development of unexposed silver halides; or physical changes in film due to e.g. heat. * In general, fog effects increase with film speed, increased development (as result of increasing development time, agitation or temperature), increased speed of development. (2). Atmospheric phenomena in which droplets of water suspended in air scatter light to varying degrees according to size and concentration of droplets and presence of other particles such as smoke or dust. * Has effect of softening details, diffusing colours, making objects seem further away -- and is extremely difficult to model digitally. (3) Clouded or diffused appearance of insufficiently polished glass. (4) The condensation of moisture on a surface, particularly an optical one.

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