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Ivana Ilic, Lorne Whitehead, Michael Webster; Contrast adaptation and illuminant spectra. Journal of Vision 2017;17(10):132. doi: 10.1167/17.10.132.
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© ARVO (1962-2015); The Authors (2016-present)
Artificial illuminants vary widely not only in their mean chromaticity but also in the range or gamut of colors they produce. For example, new high-gamut LED illuminants can expand the saturation of reds and greens by roughly 30%. We explored how the visual system might adapt to changes in the color distributions induced by different illuminants. A set of simulated surfaces (Munsell spectra) was constructed to form a uniform circle of chromaticities in cone-opponent space, when illuminated by a Plankian radiator with a color temperature of 2724 or 4000 K. Corresponding sets were then calculated for the same surfaces under a 3-primary LED spectrum with the same mean chromaticity. Observers simultaneously adapted for 3 minutes to a random sequence of the same surfaces under each pair of Plankian vs. LED sources, shown in two 4-deg fields above and below fixation. A new color was sampled from the distributions every 200 ms. Test stimuli were then shown for 500 ms in the two fields and interleaved with 4 sec of re-adaptation. The tests included 16 chromaticities uniformly sampling different chromatic angles relative to the illuminant mean. The test pair were yoked so that increasing the test contrast in the top field reduced it in the bottom field or vice versa, and observers adjusted them to match their appearance. These matches required significantly higher contrast along the reddish-greenish axis for the LED adaptation, consistent with a sensitivity loss induced by selective adaptation to the higher red-green contrast created by the LED spectra. Our results suggest that commonly available light sources may significantly alter the states of contrast adaptation in the visual system, and that this contrast adaptation is important for understanding the perceptual consequences of both short and long-term exposure to different illuminants. Funding: EY-10834
Meeting abstract presented at VSS 2017
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