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Sean F O'Neil, Michael A Webster; Filling in or filling out – color in the center of gaze. Journal of Vision 2012;12(9):1210. doi: https://doi.org/10.1167/12.9.1210.
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Uniform fields appear uniform in color despite spatial variations in spectral sensitivity owing to factors such as macular pigment screening and the absence of short-wave cones in the central fovea. We examined how color appearance varies with field size and spatial delineation to explore how the fovea and near periphery are weighted. Chromatic sensitivity is best in the fovea, and under some conditions can "fill out" to affect color percepts in the periphery. Conversely, under many conditions color at peripheral borders "fills in" to alter percepts within the field. We used blue spots presented on a CRT, chosen because when small they look distinctly different in the fovea and periphery. Appearance was assessed by matching perceived color across locations. For desaturated blue spots there is a marked shift in hue, so that fixated dots appear more purple. Consequently the Abney effect (changes in hue with saturation) is substantially stronger in the fovea. This hue shift persisted for spots up to 2 deg and thus cannot be accounted for by small-field tritanopia alone, though both S-cone and macular pigment variations may contribute. As field size is increased the hue shifts toward the peripheral percept. However, similar effects were found for uniform fields delimited by sharp luminance borders or for fields which were instead tapered with a Gaussian envelope. Moreover, the perceived shifts in hue were also substantially stronger when the spots were isoluminant with the background. Our results suggest that the color percept for large fields is more strongly weighted for the near periphery, but that this filling in is not determined by the chromatic signals at luminance borders.
Meeting abstract presented at VSS 2012
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