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Michael A. Pitts, Vicki J. Volbrecht, Lucy J. Troup, Janice L. Nerger, Melissa A. Dakin; Color appearance in the peripheral retina as a function of stimulus size and intensity under rod-bleach conditions. Journal of Vision 2005;5(8):276. doi: https://doi.org/10.1167/5.8.276.
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Changes in color appearance were investigated for a range of stimulus sizes (.098, .125, .25, .5, 1, & 2°) at four intensity levels (0.3, 1.3, 2.3, & 3.3 log td), at 10° along the horizontal meridian of the temporal retina. Stimuli were presented in a Maxwellian-view optical system, and a rod-bleach procedure was employed to eliminate rod input (approx. 99% of rod photopigment bleached). Using the ‘4+1’ color-naming paradigm (blue, green, yellow, red, and saturation), observers assigned percents to describe the color appearance of a series of monochromatic stimuli ranging from 440 to 660nm in 10 nm steps. At the two lower intensities (0.3 & 1.3 log td), systematic changes in color appearance were found for stimulus sizes ≤ .25° in two distinct spectral ranges, 490–520nm & 540–570nm. In the 490–520nm range, as stimulus size was decreased, the perception of green was reduced while the perception of yellow was enhanced. In the 540–570nm range, as stimulus size was decreased, the perception of yellow was reduced while the perception of red was enhanced. When size was kept constant, and intensity was manipulated, similar patterns were revealed. This combination of results demonstrates a size-intensity trade-off with changes of color appearance. Interestingly, the perception of blue was unaffected by manipulations of stimulus size and intensity. The reduction of green, the enhancement of red, and the dynamic changes of yellow evident for small (or dim) stimuli may explain some of the previously reported differences in the literature regarding chromatic perceptive field sizes. These changes in color appearance due to size and intensity parameters are discussed in terms of cone receptor populations as well as neural summation.
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