Film grain or
granularity is the random optical texture of processed
photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from
silver halide that have received enough photons. While film grain is a function of such particles (or dye clouds) it is not the same thing as such. It is an optical effect, the magnitude of which (amount of grain) depends on both the film stock and the definition at which it is observed. It can be objectionably noticeable in an over-enlarged photographic film photograph.