A central question in color vision is: to what extent are the unique hues tied to properties of the environment versus properties of observers? We are exploring this by asking how the unique hues vary with changes in the spectral bandwidth of the stimuli, for which environmental and physiological accounts make different predictions. Selective filtering by the lens and macular pigment differentially biases the spectrum of broader bandwidth lights relative to narrower bandwidths. We are examining the extent to which these biases influence differences in perceived hue both across individuals (who might vary in ocular pigment density) and within the same individuals at different retinal eccentricities (which differ in macular pigment density). Stimuli were roughly Gaussian spectral distributions, formed by passing light through an interference wedge masked by spatial patterns generated on an LCD panel (Bonnardel et al. Vision Research 1996). Bandwidths ranged from ∼20 nm to 80 nm (full width at half height) and were empirically matched for brightness with an achromatic background (1.7 cd/m2). Observers made unique blue, green, and yellow settings in the fovea or at 10 deg in the periphery. In a second task we also made hue matches between lights of different bandwidth. Unique hues within observers shift toward shorter wavelengths in the periphery, consistent with previous studies and in rough agreement with the differences predicted by variations in macular pigment density. Differences across observers are compared to two possible models of the unique hues (based on assuming a common set of cone ratios or a common stimulus in the environment) which differ in predicting either a decrease or increase in interobserver differences as the spectrum narrows.
- Color & optics posters
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