The purpose of this research was to evaluate the two current systems which are presently industry standards for judging test exposures which are used to determine an optimum exposure value for the Hell DC 300B/L electronic dot generating scanner: 1. The Hell System 2. The Kodak System The Hell System uses aim density measurements of specific percent dot area's or integral dot densities to obtain an optimum exposure value. The Kodak System compares the dot shape and size of complementary 95 percent and 5 percent dots to obtain an optimum exposure value. The Hell computer program test tape number 149 is used to expose a variety of test patterns onto the film which is used to evaluate the dot structure and scanner calibration. Depending on the Kodak or Hell system for evaluation, the dot shape and size of a 95 percent and 5 percent dot or an integral dot density value is used to determine the correct light on film value for the correct exposure from the scanner. Light on film (LOF) is a relative value used to read the intensity or exposure of the laser light source. Six different film and developer combinations were evaluated using both systems to determine the effects of exposure on different films, developers, and at different screen rulings. An evaluation experiment was completed to determine whether the Kodak System or the Hell System is more precise for determining an optimum exposure value. Thirty viewers were asked to evaluate test exposures from a particlar film and developer combination (Kodak ES Scanner Film, Kodak Rapid Scanner Developer). Statistical analysis was used to find the variability of each system for determining the correct exposure value. The results from the testing concluded that different film, developer, and screen rulings have an affect on the optimum exposure value determined by the Hell and Kodak Systems. Secondly, the Hell System is more precise for determining an individual exposure value than the Kodak System. The Kodak System, however, was judged more versatile because it can also be used to evaluate changes in dot sharpness. A complete set of separations were also made. Kodak ES Scanner Film and Kodak Rapid Scanner Developer was used to make three separations with different exposure values to determine the effects of exposure on the printed separations. An evaluation experiment was completed to determine which separation gave the best results. Thirty viewers used a paired comparison evaluation procedure to determine which LOF value gave the preferred results. However, neither the Kodak or the Hell methods were valid according to the results. The printed separations indicated that exposure causes detectable differences between the printed separations. Based upon the results of the separations, neither the Kodak System or the Hell System to determine the correct LOF produced the optimum results on the Hell DC 300 B/L Scanner as determined by the control group of observers.
Library of Congress Subject Headings
Electronics in color printing--Methods--Evaluation; Color separation--Methods--Evaluation; Color printing--Methods--Evaluation
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
DeMuth, Randy, "Dot structure analysis of film and developer combinations to optimize LOF for the DC-300B/L scanner" (1985). Thesis. Rochester Institute of Technology. Accessed from
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