Wavelength-selective filtering by the lens and macular pigment biases the spectra of broadband lights more than narrowband. We asked to what extent these filtering effects influence the perceived hue of a light as its bandwidth is varied. Previously we approached this question by comparing individual differences in unique hues as a function of bandwidth (Mizokami et al., JOV 2002). In the present study we instead sampled a range of spectral stimuli with a hue-matching task. Spectra were created by dispersing light with an interference wedge and then filtering by spatial masks on an interposed LCD panel (Bonnardel et al., Vision Research 1996). The lights were displayed as a uniform 2-deg field formed by the aperture of an integrating sphere. Subjects viewed the field directly or at an eccentricity of 10 deg. Reference stimuli had a fixed dominant wavelength and a roughly Gaussian spectrum with a bandwidth of 105 nm. Test stimuli had a bandwidth of 25 nm or greater. On each trial the two lights were shown in succession. The dominant wavelength of the narrower bandwidth was varied in a 2AFC staircase to match the pair for hue. We compare these matches to the predicted spectra required to maintain a fixed direction in cone-excitation space. Results suggest a weak but incomplete influence of pigment screening at shorter wavelengths, suggesting partial compensation for the filtering effects of the eye.
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