Development adjacency effects and optical spread in photographic systems cause difficulties in predicting small-scale densities. These effects can be quantified as spread functions. The optical spread func tion describes the light scatter of the film. The chemical spread func tion describes the lateral diffusion of development- inhibiting and dev elopment-accelerating reaction products. These spread functions can be used along with the sensitometry and covering power relationships of the system to predict small-area densities from the object exposure profile. A study based on C. N. Nelson\u27s work was undertaken to develop a math ematical model that uses the optical and chemical spread functions to predict small-area densities of an image from the original object ex posure profile. This model was developed for a fine-grain aerial dup licating film processed in KODAK D-76 (1:4). It was found that the model predicted the image profile of a log-periodic target to within 0.02 D on the peaks of the bars. However, the model overshot the edges of the bars by about -0.0$ D. This difference, even though significantly greater than the experimental error, does not affect the usefulness of this model to image quality studies
