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Heuristic model for understanding x‐ray film characteristics
Author(s) -
Dixon Robert L.,
Ekstrand Kenneth E.
Publication year - 1976
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.594264
Subject(s) - photographic emulsion , emulsion , optics , materials science , exponential function , attenuation , heuristic , grain size , mathematics , physics , mathematical analysis , composite material , chemistry , mathematical optimization , biochemistry , silver halide
A simple, heuristic model of a photographic emulsion is described for the purpose of illustrating the fundamental physical processes and emulsion properties which determine the characteristics of an x‐ray film (viz., the shape of the H − D curve, film gamma, and film speed). By means of this model, it is shown that the contrast multiplication afforded by an x‐ray film (i.e., a film gamma greater than unity) is a direct result of the exponential attenuation of the viewing light by the developed film, and that film gamma is proportional to grain size, grain density, and emulsion thickness. The difference in the H − D curve that is observed when the same film is exposed to light from an intensifying screen or directly to x rays is also predicted by the model.