More Definitions!

Film Grain:  random optical texture of processed photographic film due to the presence of small grains of a metallic silver developed from silver halide that have received enough photons. (source)

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Digital Noise: random variation of brightness or color information in images produced by the sensor and circuitry of a scanner or digital camera. (source)

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• also originates in film grain and in the unavoidable shot noise of an ideal photon detector (source)