Markov Photographic Noise

Photographic noise is studied from the point of view of continuous-parameter Markov chains. A general, conditional-probability distribution of the undeveloped grains in a cell is used for a pure-death process. The corresponding mean and variance are obtained. A new theoretical expression relating rms density to average density is also determined. The application of this probability distribution to a typical photographic film is demonstrated and the informational sensitivity, defined for the effectiveness of information transmission, is also derived. Finally, it is concluded that the photographic process is nonhomogeneous in the sense that the probability of grain development (death) is a function of exposure time.