Separate processing of chromatic and achromatic contrast in color constancy
article
In a preceding study we measured human color constancy in experimental conditions in which simulated illuminants and surface colors were varied in the chromatic domain only. Both illumination level and sample re.ectance were fixed in that study. In the present study we focus on the achromatic dimension, both with respect to luminance contrast (Experiment 1) and overall illumination (Experiment 2). Sample-to-background contrast was varied over a two log unit range that covered both luminance decrements and increments. Illumination level was varied either for the short-wave-sensitive (S) cones only or for all three cone types simultaneously. Data predictions on the basis of a cone-specific response function, derived in our preceding study, indicate that this model has difficulty in accommodating the results obtained with varying luminance contrast.
However, a modified version of the response function, incorporating separate processing of color and luminance contrast, correctly predicts the data from both the present and the previous study. We also show that over a limited stimulus range our earlier response function is mathematically equivalent to Jameson and Hurvichs model of brightness contrast. The latter model, cast into a trichromatic format, performs equally well or better than our original response function, but is less accurate than our modified model.
(so-called designators) are computed that register the
perceived color as a point in a three-dimensional lightness
However, a modified version of the response function, incorporating separate processing of color and luminance contrast, correctly predicts the data from both the present and the previous study. We also show that over a limited stimulus range our earlier response function is mathematically equivalent to Jameson and Hurvichs model of brightness contrast. The latter model, cast into a trichromatic format, performs equally well or better than our original response function, but is less accurate than our modified model.
(so-called designators) are computed that register the
perceived color as a point in a three-dimensional lightness
Topics
colour contrastcolourBrightness modelColor constancyCone-specific contrastLuminance contrastLuminance normalizationColor matchingFunctionsLight reflectionLightingLuminescenceMathematical modelsMathematical transformationsPattern matchingPhotochromismAchromatic contrastBrightness modelChromatic contrastColor constancyCone-specific contrastLuminance contrastLuminance normalizationResponse functionColor vision
TNO Identifier
13545
Source
Color Research and Application, 30(3), pp. 172-185.
Pages
172-185
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