The energy ratios of yellow to blue monochromatic lights at the yellow/blue equilibria (appearing neither yellowish nor bluish) were investigated for two color-normals along the horizontal meridian of the temporal retina at the fovea (0°), parafovea (3.3°), and near periphery (10°) of the left eye. The stimulus size was enlarged with retinal eccentricity according to the cortical magnification factor (
M-scaling). It was found that the relative energy ratios at the yellow/blue equilibria were constant at the three retinal locations investigated. Thus, the yellow/blue equilibrium hue judgements are not affected by the preretinal filtering effect of macular pigment, which means that the yellow-blue (
y-b) opponent-color system modifies its relative responses to compensate for the effect of macular pigment. On the other hand, the sensitivities of the achromatic system measured by heterochromatic flicker photometry, using similar yellow and blue monochromatic lights (570 and 470 nm, respectively), are affected by macular pigment. These results suggest the existence of the counterbalancing mechanism for color perception against macular pigment in the
y-bsystem.
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