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Colour appearance and compensation in the near periphery.

Webster MA, Halen K, Meyers AJ, Winkler P, Werner JS - Proc. Biol. Sci. (2010)

Bottom Line: However, adjusting only to the average stimulus cannot correct for all of the effects of a spectral sensitivity change, and predicts differences in colour percepts between the fovea and periphery that were not observed.The similarities in hue percepts at 0 and 8 degrees thus suggest that additional processes help compensate colour appearance to maintain constancy in the near periphery.We model the results of previous studies to show that similar adjustments are implied by age-related changes in lens pigment, and to show that these adjustments are consistent with previous measurements of peripheral colour appearance based on hue cancellation.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Nevada, Reno, NV, USA. mwebster@unr.edu

ABSTRACT
The spectral sensitivity of the visual system varies markedly between the fovea and surrounding periphery owing in part to the rapid fall in macular pigment density with eccentricity. We examined how colour appearance changes between the fovea and near periphery (8 degrees) by measuring achromatic loci and the loci of unique and binary hues. Chosen colours remained much more similar at the two locations than predicted by the change in spectral sensitivity. Compensation for white may reflect long-term gain changes within the cones that equate sensitivity for the local average stimulus in the fovea and periphery. However, adjusting only to the average stimulus cannot correct for all of the effects of a spectral sensitivity change, and predicts differences in colour percepts between the fovea and periphery that were not observed. The similarities in hue percepts at 0 and 8 degrees thus suggest that additional processes help compensate colour appearance to maintain constancy in the near periphery. We model the results of previous studies to show that similar adjustments are implied by age-related changes in lens pigment, and to show that these adjustments are consistent with previous measurements of peripheral colour appearance based on hue cancellation.

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(a) Achromatic settings for eight observers at the fovea (open circles) or 8° (filled triangles). Lines connect settings for each observer. Filled diamonds: predicted change in periphery assuming no compensation for macular screening and a pigment density difference of 0.15, 0.3 or 0.45. Open diamonds: predictions if only the S cones are compensated. (b) LvsM (filled circles) or SvsLM (open triangles) coordinates in the fovea or periphery.
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RSPB20091832F1: (a) Achromatic settings for eight observers at the fovea (open circles) or 8° (filled triangles). Lines connect settings for each observer. Filled diamonds: predicted change in periphery assuming no compensation for macular screening and a pigment density difference of 0.15, 0.3 or 0.45. Open diamonds: predictions if only the S cones are compensated. (b) LvsM (filled circles) or SvsLM (open triangles) coordinates in the fovea or periphery.

Mentions: The first measurements replicated studies of white settings in the fovea and periphery (Beer et al. 2005; Webster & Leonard 2008). Figure 1 compares these settings to the differences predicted if there were no compensation for macular pigment or compensation only within S cones, based on adjusting the cone sensitivities (Smith & Pokorny 1975) by the macular pigment transmittance function (Bone & Sparrock 1971) scaled for a peak density of 0.3 ± 0.15 (consistent with the average difference for our observers). The foveal white point was assumed to correspond to illuminant E, and the monitor chromaticity required to generate the same cone ratios in the periphery was then calculated either without renormalizing the cones or renormalizing the S cones so that its mean response to an equal-energy spectrum equaled the foveal response.


Colour appearance and compensation in the near periphery.

Webster MA, Halen K, Meyers AJ, Winkler P, Werner JS - Proc. Biol. Sci. (2010)

(a) Achromatic settings for eight observers at the fovea (open circles) or 8° (filled triangles). Lines connect settings for each observer. Filled diamonds: predicted change in periphery assuming no compensation for macular screening and a pigment density difference of 0.15, 0.3 or 0.45. Open diamonds: predictions if only the S cones are compensated. (b) LvsM (filled circles) or SvsLM (open triangles) coordinates in the fovea or periphery.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2871866&req=5

RSPB20091832F1: (a) Achromatic settings for eight observers at the fovea (open circles) or 8° (filled triangles). Lines connect settings for each observer. Filled diamonds: predicted change in periphery assuming no compensation for macular screening and a pigment density difference of 0.15, 0.3 or 0.45. Open diamonds: predictions if only the S cones are compensated. (b) LvsM (filled circles) or SvsLM (open triangles) coordinates in the fovea or periphery.
Mentions: The first measurements replicated studies of white settings in the fovea and periphery (Beer et al. 2005; Webster & Leonard 2008). Figure 1 compares these settings to the differences predicted if there were no compensation for macular pigment or compensation only within S cones, based on adjusting the cone sensitivities (Smith & Pokorny 1975) by the macular pigment transmittance function (Bone & Sparrock 1971) scaled for a peak density of 0.3 ± 0.15 (consistent with the average difference for our observers). The foveal white point was assumed to correspond to illuminant E, and the monitor chromaticity required to generate the same cone ratios in the periphery was then calculated either without renormalizing the cones or renormalizing the S cones so that its mean response to an equal-energy spectrum equaled the foveal response.

Bottom Line: However, adjusting only to the average stimulus cannot correct for all of the effects of a spectral sensitivity change, and predicts differences in colour percepts between the fovea and periphery that were not observed.The similarities in hue percepts at 0 and 8 degrees thus suggest that additional processes help compensate colour appearance to maintain constancy in the near periphery.We model the results of previous studies to show that similar adjustments are implied by age-related changes in lens pigment, and to show that these adjustments are consistent with previous measurements of peripheral colour appearance based on hue cancellation.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of Nevada, Reno, NV, USA. mwebster@unr.edu

ABSTRACT
The spectral sensitivity of the visual system varies markedly between the fovea and surrounding periphery owing in part to the rapid fall in macular pigment density with eccentricity. We examined how colour appearance changes between the fovea and near periphery (8 degrees) by measuring achromatic loci and the loci of unique and binary hues. Chosen colours remained much more similar at the two locations than predicted by the change in spectral sensitivity. Compensation for white may reflect long-term gain changes within the cones that equate sensitivity for the local average stimulus in the fovea and periphery. However, adjusting only to the average stimulus cannot correct for all of the effects of a spectral sensitivity change, and predicts differences in colour percepts between the fovea and periphery that were not observed. The similarities in hue percepts at 0 and 8 degrees thus suggest that additional processes help compensate colour appearance to maintain constancy in the near periphery. We model the results of previous studies to show that similar adjustments are implied by age-related changes in lens pigment, and to show that these adjustments are consistent with previous measurements of peripheral colour appearance based on hue cancellation.

Show MeSH