With the advent of the spectrophotometer as an alternative to the densitometer for pressroom applications, it becomes desirable to use a single three-color overprint halftone gray patch for controlling color on the press. As a consequence, the need for new specifications in colorimetric units, rather than SID and dot gain units, arises. The purpose of this study was to conduct a mathematical conversion of the traditional SID and dot gain specifications into the colorimetric specifications, in terms of the CIELAB coordinates. The FIPP dot gain and SID specifications were applied to the gray patch contained in the Gretag CMS3 color control bar. This gray comprises an overprint of 75% cyan, 62% magenta, and 60% yellow. Applying all possible SID and dot gain tolerances to this gray results in overall 225 three-color overprint grays. By employing computer programs containing the GRL Trapping Model, (2) the GRL Dot Gain Model, and (3) the Yule-Nielsen modified Spectral Neugebauer Model, the CIELAB coordinates of the 225 grays were predicted without taking actual spectrophotometric measurements on press sheets. The CIELAB coordinates of these grays were then plotted in the three-dimensional L* a* b* space. The shape of the cluster of these 225 grays is nearly spherical. The largest deviation of one of XI these grays from the aim gray is 4.7 AE*ak units. Varying any dot area by ± 2% or changing any SID by ± 0.1 causes a color deviation of less than 3 (delta)E*ab units.

Library of Congress Subject Headings

Electronics in color printing; Color printing; Colorimetric analysis

Publication Date


Document Type


Department, Program, or Center

School of Print Media (CIAS)


Sigg, Franz

Advisor/Committee Member

Viggiano, J. Stephen


Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: Z258.T36 1993


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