'GRATR' A Tone Reproduction Model; Illustrating the Conventional and GCR Offset Lithographic Web Printing Process

An improved Jones [1], tone reproduction system the Graphic Regression Analysis Tone Reproduction or 'GRATR' model is detailed. Examples of the use of this model in describing the 4 color conventional and GCR positive acting offset lithographic printing process are reviewed. Using the 'GRATR' model the photomechanical reproduction cycle is followed from the original transparency through electronic scanning to ink on paper reproduction. The use of regression analysis to obtain the tone reproduction curves is introduced and mathematical expressions derived that can be used to model the process detailed. Such work will help users understand scanners, films, print, plate and press interaction properties as they relate to print properties and other factors.