198 Munsell samples, representing 13 hues at various value levels and chromas, including 9 neutrals, were viewed separately on black, gray, and white backgrounds under Illuminant A and matched by samples viewed in Illuminant C by 7 observers, making a total of over 4000 matchings. With these samples, hues containing red and blue become redder in Illuminant A as compared with Illuminant C, while hues from Munsell purple-blue to yellow-red shift toward reddish yellow. Two invariant hues emerge, one between 10R and 5YR with all backgrounds, the other between 5PB and 10B with white background, and between 5PB and 10B with gray and black backgrounds. Greatest shifts occur with black background, least with white. General trends are qualitatively in accord with the Helson-Judd principles of color conversion and in the direction to be expected from the I.C.I. specifications of the samples in the two illuminants. The changes in hue and chroma and the invariant hues as they appear in the I.C.I. plots are not far different from those observed, but the computed changes are much greater than the observed because the I.C.I. computations are based on a completely non-reflecting background and observers screened from the illuminants. Further theoretical treatment of the data seems warranted.
© 1947 Optical Society of AmericaFull Article | PDF Article
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