Two methods were attempted to determine an objective evaluation of lithographic films with respect to the sharpness of half-tone dots produced by the films. In Method I a step function target was placed in contact with a continuous wedge and a film sample. After exposure and development, a curve of the film was drawn in terms of per cent transmission versus log exposure. Since the input (target) is a step function, the output (curve) should also be a step function. It was expected that the width of the step in the curve would yield some measure of how well the film would produce hard dots. After curves for several films were drawn and examined, it was found that there was no difference between films. Method II was conducted in a similar way as Method I but a different target was used. A line screen was used to expose a film in such a way that the lines ran parallel to the sample. The target was then turned ninety degrees and a second sample was exposed. After development, the film was analyzed to find a difference in curves caused by the target orientation. This difference was compared with the difference obtained with another film. No difference between the films was found.
Library of Congress Subject Headings
Photographic sensitometry; Images, Photographic
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
McCreary, Timmy, "A Method of Determining Dot Sharpness of Lithographic Films" (1973). Thesis. Rochester Institute of Technology. Accessed from
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