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Rigmor C. Baraas, David H. Foster, Kinjiro Amano, Sérgio M. C. Nascimento; Dichromatic judgments of surface color under different illuminants on natural scenes. Journal of Vision 2005;5(8):1022. doi: 10.1167/5.8.1022.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this study was to test dichromats' ability to judge surface color under different illuminants on natural scenes. Stimuli were simulations of natural scenes presented on a high-resolution color monitor with 10-bit resolution per gun. Twenty-two scenes (which included rocks, foliage, and buildings) were obtained with a hyperspectral imaging system (Foster et al., 2004, Visual Neurosci., 21, 331–336). Illuminants were drawn from the daylight locus. In each trial, two images were presented in sequence, each for 1 s, with no interval: in the first image, the correlated color temperature of the illuminant was 25000 K or 4000 K, in the second, it was 6700 K. The spectral reflectance of a surface in the second image was changed randomly, from trial to trial. The size and position of the test surface, which was indicated to the observer, varied with the scenes tested. The observer's task was to decide whether the test surface in the successive images was the same. Six deuteranopes, eight protanopes, and two tritanopes participated in the study.
A preliminary analysis suggested that deuteranopes could judge surface colors about as well as normal trichromats for about half of the natural scenes tested; with protanopes it was for rather fewer scenes, and with tritanopes fewer still. The two tritanopes' overall performance was also more variable than that of red-green dichromats. Why tritanopes might be particularly disadvantaged is unclear, since similar experiments with Mondrian-like patterns of Munsell surfaces (Foster et al., 2003, in Normal & Defective Colour Vision Eds J D Mollon, J Pokorny and K Knoblauch (Oxford: Oxford), pp 218–224) suggest that short-wavelength-sensitive cones make only a small contribution to surface-color judgments.
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