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Proceedings Paper

Color sameness: what to do when Grassmann additivity fails experimentally
Author(s): Michael H. Brill
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Paper Abstract

Device-independent color reproduction depends on matching colors that arise from different spectral power distributions. The spectral differences of matching lights are particularly great between light produced by VDU phosphors and light reflected by pigmented materials. The least frequently questioned assumption in this difficult situation is the Grassmann additivity rule, that if matching lights are added to two sides of a match, the result is also a match. However, recent experiments by Thornton suggest there is strong Grassmann additivity failure for human color vision. In particular, a color-match of a test light with one set of primaries does not persist when each of these primaries is replaced by a matching mixture of a second set of primaries. The present paper examines two covering theories for Grassmann additivity in search of consistency with Thornton's results. The theories are as follows: (1) Power- function theory. Each cone performs a weighted wavelength sum of an exponentiated value of photon flux over wavelength (not simply a weighted count on the photons, in which the implicit exponent is 1); and (2) Photodepletion theory. The density of unbleached photopigment in a cone is decreased under the action of light, and this leads to an integral- equation expression for the quantum catch instead of a simple spectrum integral. When Thornton's color-matching data are examined in terms of both these theories, the conventional Grassmann theory is found to fit the data best.

Paper Details

Date Published: 4 August 1993
PDF: 10 pages
Proc. SPIE 1909, Device-Independent Color Imaging and Imaging Systems Integration, (4 August 1993); doi: 10.1117/12.149083
Show Author Affiliations
Michael H. Brill, Science Applications International Corp. (United States)

Published in SPIE Proceedings Vol. 1909:
Device-Independent Color Imaging and Imaging Systems Integration
Ricardo J. Motta; Hapet A. Berberian, Editor(s)

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