The Effects of Luminance Boundaries on Color Perception
Annual rept. 15 Mar 1990-14 Mar 1991,
HARVARD UNIV CAMBRIDGE MA DIV OF APPLIED SCIENCES
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When a suprathreshold luminance flash, presented as an increment on a large background field, accompanies a coincident equiluminant flash, the chromatic threshold is reduced. Early studies suggested that the chromatic facilitation grows large at small test size. We have measured detection thresholds for test spots with diameters from 5 min - 1 degree. Even for the smallest size the chromatic red-green sensitivity specified in cone-contrast coordinates is greater than luminance sensitivity, which has important implication for what the eye sees best. Facilitation by the luminance flash remains constant at 2x for all sizes contrary to other earlier studies. Further work with 1 degree flashes indicates that the facilitation results from a demarcation of the chromatic region by luminance features, and is not due to simple reduction of detection uncertainty. We also studied how the L and M cone signals combine in detecting motion.