Proceedings PaperColor scanner calibration of reflected samples
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This paper presents a methodological approach for integrating non-colorimetric scanners with CIE standards as a means toward a device independent process. The calibration is aimed at reflected samples by employing photographic, thermal transfer, and xerographic prints. Correlations between scanner responses to CIE standards are established through a common test object using a two-step process of the gray balancing and the matrix transformation. A series of polynomials, ranging from a three-term linear combination to a twenty-term cubic equation, is used for converting device values to a CIE color space. The ability to fit colors that are not in the training set by a polynomial is examined. Results indicate that lower order polynomials fit colors equally well whether a color is in the training set or not, but the accuracy of interpolation decreases as the number of terms in the polynomial increases. We study the generality of this calibration method with respect to input materials. The transformation is material-dependent. Within the experimental uncertainty, however, there exists a unified transfer matrix for photographic materials and another one for paper substrates. Finally, we extended this method to deal with the mismatched illuminants for viewing and calibration. An empirical white point conversion method is proposed and tested; good approximations to the measured results are obtained when the interchange of illuminants occurs.