Abstract
Abstract: :
Purpose: The purpose of this study was to assess the influence of rods on color appearance by comparing perceptive field sizes obtained under conditions designed to eliminate rod contribution to those obtained when rods are active in color judgements. Methods: Perceptive field sizes of blue, green, yellow, and red were determined for 4 observers in the fovea and at 10 in the temporal retina using a standard color-naming procedure. Stimuli ranging from 440 - 660 nm were equated at 20 td and were presented for 500 ms with an 18 s ISI. Test size varied from 0.10 - 3.0 for the bleach conditions and 0.25 - 3.0 for the no-bleach trials. Color-naming functions were obtained after 10 min dark adaptation for both the fovea and the no-bleach peripheral conditions. For the bleach condition, observers viewed a 20, 7.32 log scotopic td broadband field for 10 s resulting in a 99.8% rod photopigment bleach. Following the rod bleach, observers made hue and saturation determinations on the cone plateau. Perceptive field sizes were determined by fitting a Michaelis-Menten growth function to the color naming data scaled to saturation. Results: Consistent with previous studies, stimuli under the no-bleach condition in the peripheral retina appeared less saturated than stimuli in the other two conditions. Perceptive field sizes in the fovea were smaller than in the peripheral retina. More interestingly, perceptive field sizes for all four hues were smaller in the peripheral retina by at least a factor of 10 when rod signals were minimized. This decrease in size was even greater for blue and green perceptive fields. Conclusion: Perceptive field sizes for all four elemental hues are smaller when rod contribution is minimized. Thus, the effects of rods on peripheral color perception are to decrease saturation and increase the perceptive field sizes for all four elemental hues.
Keywords: 362 color vision • 360 color appearance/constancy