A new procedure for obtaining the Chemical Spread Function of an emulsion-developer combination is discussed. This procedure consists of directly measuring the Optical Modulation Transfer Function (MTFO) by scanning the sinusoidal object irradiance distribution through the non-developed emulsion using a microdensitometer. The Modulation Transfer Function (MTF) of the processed emulsion is determined in the conventional manner. Then the Chemical Modulation Transfer Function (MTFC) is determined from the linear relationship: MTF = MTFC X MTFO. Once the MTFO is determined then the Spread Function is calculated using the Fourier Transform operator. Photographic systems are in general non-linear. However it is well known that for moderate input modulation and relatively small gamma the photographic material acts linearly. Results are obtained for Kodak High Contrast Copy film 5069 processed in Kodak D-76 developer. It is concluded that this method can be used to determine the Chemical Spread Function of more widely used film-developer combinations. Recommendations are made for improvement to the method to obtain more accurate results.
Library of Congress Subject Headings
Photographic emulsions; Photographic optics; Transfer functions
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Laitre, J.N.A., "Determination of the chemical spread function of Kodak High Contrast Copy 5069 Emulsion" (1979). Thesis. Rochester Institute of Technology. Accessed from
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