Separate processing of chromatic and achromatic contrast in color constancy

Lucassen, Marcel P.; Walraven, Jan

doi:10.1002/col.20105

Cited by 8 publications

(5 citation statements)

References 51 publications

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“…As already indicated, the properties considered were of two kinds: one was colorimetric, based on CIELAB lightness L *, hue h ab , and chroma C * ab (which correlates with colorfulness as a proportion of the brightness of a similarly illuminated area that appears white; see e.g., Fairchild (2005)); the other was receptor-based, involving simple combinations of excitations in long-, medium-, and short-wavelength-sensitive cones (L, M, and S), calculated as in Foster et al (2004). As a result of previous work, one of these receptoral properties included the spatial ratio of cone excitations between pairs of points in the image (Foster & Nascimento, 1994; Nascimento & Foster, 1997), although here evaluated over all surfaces rather than just between the test surface and other surfaces or averages over surfaces in the scene (Amano & Foster, 2004), possibly in some nonlinear form (Lucassen & Walraven, 1993, 2005). Differences in ratios across images were calculated in the following way (Nascimento & Foster, 1997).…”

Section: Methodsmentioning

confidence: 99%

Color constancy in natural scenes explained by global image statistics

2006

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To what extent do observers' judgments of surface color with natural scenes depend on global image statistics? To address this question, a psychophysical experiment was performed in which images of natural scenes under two successive daylights were presented on a computer-controlled high-resolution color monitor. Observers reported whether there was a change in reflectance of a test surface in the scene. The scenes were obtained with a hyperspectral imaging system and included variously trees, shrubs, grasses, ferns, flowers, rocks, and buildings. Discrimination performance, quantified on a scale of 0 to 1 with a color-constancy index, varied from 0.69 to 0.97 over 21 scenes and two illuminant changes, from a correlated color temperature of 25,000 K to 6700 K and from 4000 K to 6700 K. The best account of these effects was provided by receptor-based rather than colorimetric properties of the images. Thus, in a linear regression, 43% of the variance in constancy index was explained by the log of the mean relative deviation in spatial cone-excitation ratios evaluated globally across the two images of a scene. A further 20% was explained by including the mean chroma of the first image and its difference from that of the second image and a further 7% by the mean difference in hue. Together, all four global color properties accounted for 70% of the variance and provided a good fit to the effects of scene and of illuminant change on color constancy, and, additionally, of changing test-surface position. By contrast, a spatial-frequency analysis of the images showed that the gradient of the luminance amplitude spectrum accounted for only 5% of the variance.

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Section: Methodsmentioning

confidence: 99%

Color constancy in natural scenes explained by global image statistics

2006

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“…This implies in turn that if L and M contrasts are linear functions (holding constant for given objects and their matches), the match must be based on luminance contrast since the luminance signal depends on L/M cone signals (Luminance 1.6L M) [35,37]. Somehow the cone-contrast system seems unable to cope with this information, perhaps because the luminance signal adds vectorally.…”

Section: A Chromatic and Achromatic Aspects Of Color Constancy And Tmentioning

confidence: 99%

Systematic violations of von Kries rule reveal its limitations for explaining color and lightness constancy

Kulikowski

Daugirdienė²,

Panorgias

et al. 2012

J. Opt. Soc. Am. A

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Cone contrast remains constant, when the same object/background is seen under different illuminations-the von Kries rule [Shevell, Vis. Res. 18, 1649 (1978)]. Here we explore this idea using asymmetric color matching. We find that von Kries adaptation holds, regardless of whether chromatic constancy index is low or high. When illumination changes the stimulus luminance (reflectance), lightness constancy is weak and matching is dictated by object/background luminance contrast. When this contrast is masked or disrupted, lightness constancy mechanisms are more prominent. Thus von Kries adaptation is incompatible with lightness constancy, suggesting that cortical mechanisms must underlie color constancy, as expected from neurophysiological studies [Zeki, Nature 284, 412 (1980); Wild, Nature 313, 133 (1985)].

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“…2 Perhaps this is natural, given evidence for the independence of color and luminance detection mechanisms 3 and that chromatic and achromatic contrasts have separate effects on color constancy. 4 Yet in principle, color constancy and brightness constancy must be related, as argued here. Note that when test samples are exposed in complex surrounds, task instructions differentiate brightness from lightness 2 and paper matches, i.e., matches for samples "seen as if they were the same piece of paper under different illuminants," from direct matches of chromaticity, 1 but in the following the terms "brightness" and "color" are used generically since the argument of the paper applies no matter the task.…”

mentioning

confidence: 81%

“…For example, the line of empirical research using Mondrian displays that was began by Arend and Reeves ignored brightness when measuring color and ignored color when measuring brightness . Perhaps this is natural, given evidence for the independence of color and luminance detection mechanisms and that chromatic and achromatic contrasts have separate effects on color constancy . Yet in principle, color constancy and brightness constancy must be related, as argued here.…”

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confidence: 90%

The dependence of color constancy and brightness constancy on saturation

Reeves

2018

Color Research & Application

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Color constancy and brightness constancy are not independent, as often assumed, since increasing sample saturation decreases the demand on color constancy mechanisms and increases the demand on brightness constancy mechanisms made by changes in illuminant color temperature. Re-analyzed published data illustrates these tendencies for low saturations, but comprehensive measurements will be needed to pin down the postulated relationships over the full range. K E Y W O R D Scolor appearance, color constancy, color temperature Color Res Appl. 2018;1-3.wileyonlinelibrary.com/journal/col

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Separate processing of chromatic and achromatic contrast in color constancy

Cited by 8 publications

References 51 publications

Color constancy in natural scenes explained by global image statistics

Color constancy in natural scenes explained by global image statistics

Systematic violations of von Kries rule reveal its limitations for explaining color and lightness constancy

The dependence of color constancy and brightness constancy on saturation

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