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Volume: 13 | Article ID: art00033
A Variational Link of Marking to Color for Color Printing Technologies: The Color Gain Matrix for the Simple Estimation of Print to Print Variation
  DOI :  10.2352/CIC.2005.13.1.art00033  Published OnlineJanuary 2005

Profitable print image reproduction is highly dependent upon print to print and between print run variability. This paper presents methods extracted from process control technology and linear systems to provide a powerful, yet simple, method of estimating printing color white noise (print to print variability). These methods are then utilized to estimate mean color white noise (in ΔEab), along the neutral axes for both the CGATS SWOP TR001 and the CGATS SWOP TR004 offset press standards. Given a known uncertainty in separation marking, local color white noise is immediately available. Both correlated and uncorrelated variation in c,m,y are considered.Total color error emanating from correlated fluctuations in c,m,y and uncorrelated fluctuations in c,m,y are computed and presented. Contrary to many natural systems where all variables are subject to positive or zero variability, uncorrelated error exceeds correlated error.Partial differential linearization methods are utilized to quantitatively compute color gain, and color error, associated with forced changes in marking digital count (uncertainty in marking). These linearization methods are applied along the neutral axes of the SWOP TR004 and SWOP TR001 four color presses. From each linearization term a gain matrix associated with each separation can be extracted. This gain matrix provides, at a glance, the variational structure of color for changes in marking. Having constructed a Jacobian, relating L*a*b* to variational terms in c,m,y, the overall Euclidean, correlated and uncorrelated, color error can be computed for a given local marking fluctuation in c,m,y.These methods, commonly utilized to estimate local control point stability of process control systems in the process industry and electronics, provide simple and powerful methods for estimating color stability around local points in color space for digital printing. Given the importance of estimating print to print variability for given colorant and halftone, these methods are powerful and do not require the print and measurement of thousands of prints to extract.The neutral axes of a c,m,y color space employs all three separations along a critical line where the eye is most sensitive to color variation. Hence, it is this axis for which the techniques developed are applied. Color gain is computed in increments of 5 L*, beginning at L*=95 along the neutral axes of the SWOP TR001 and SWOP TR004 specification.A comprehensive comparison of the neutral axes of both TR001 and TR004 specifications is a byproduct of the development of color gain.

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Michael Sanchez, Martin Maltz, "A Variational Link of Marking to Color for Color Printing Technologies: The Color Gain Matrix for the Simple Estimation of Print to Print Variationin Proc. IS&T 13th Color and Imaging Conf.,  2005,  pp 171 - 184,

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