A COMPUTER PROGRAM TO DETERMINE PHOTOGRAPHIC EMULSION CALIBRATION CURVES

The two-line method of emulsion calibration is used to produce a set of related transmittance readings for a pair of homologous iron lines bearing a fixed ratio of intensity to each other. These data are converted to Seidel densities and fitted to a linear regression equation. This preliminary curve equation is utilized to select a set of transmittances to be correlated with a series of relative intensities which are an exponential function of the line pair intensity ratio. This data output, which is the final H & D curve, is then fitted to two curvilinear regression equations which are required to intersect at 50.0 % transmittance. The equations are normalized to produce relative intensities from 100.0 to about 1.0 for transmittances from 1.0 to 99.9%. The coefficients are then employed to generate tables which indicate a relative intensity for all transmittances from 1.0 to 99.9 % in increments of 0.1 % transmittance. The program is suitable for any emulsion calibration using Seidel density in conjunction with linear preliminary curves and where the intensity function is derived from a geometric or exponential series. © 1969.