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Avery Krieger, Hilary Dubin, Bradley Pearce, Stacey Aston, Anya Hurlbert, David Brainard, Ana Radonjić; Illumination discrimination depends on scene surface ensemble. Journal of Vision 2015;15(12):403. doi: https://doi.org/10.1167/15.12.403.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to discriminate between scenes under different illuminations may provide insight into how the visual system represents and perhaps discounts changes in illumination (Pearce et al. 2014). Here we examine whether there is an interaction between sensitivity to illumination changes in different chromatic directions and the chromaticity of the surfaces in the scene. Simulated stimulus scenes were rendered hyperspectrally using RenderToolbox3 and displayed stereoscopically. Each scene was specified as a room covered with rectangular, uniform matte surfaces of widely different colors. Across the three surface ensembles used, the shape and position of surfaces was fixed but their assigned surface reflectance varied. Under simulated illuminant D67, one surface ensemble was roughly ‘neutral’ in average chromaticity (mean xy: [0.32, 0.35]), while the other two were ‘reddish-blue’ ([0.36, 0.34]) and ‘yellowish-green’ ([0.39, 0.42]) relative to it. For each ensemble we measured illumination discrimination thresholds along four different chromatic directions (‘blue’, ‘yellow’, ‘red’ and ‘green’) using a staircase procedure. The subjects viewed the target scene (simulated illuminant D67) and two comparison scenes — one identical to the target and another rendered under the test illuminant — and judged which of the comparison scenes matched the target. Varying average scene chromaticity had an effect on illumination discrimination thresholds, and that effect was different for different illuminant-change directions. Notably, thresholds for the ‘blue’ illumination-change direction were higher for the ‘yellowish-green’ surface ensemble than for the ‘neutral’ (+5.6∆E) and ‘reddish-blue’ (+6.1∆E) ensembles, while thresholds for the ‘red’ illumination change-direction were lowest for the ‘reddish-blue’ ensemble (-3.7∆E relative to the ‘neutral’; -4.1∆E relative to the ‘yellowish-green’ ensemble). Our results show that characterization of illumination discrimination must take the scene surface ensemble into account, and that the relative discriminability of illumination changes in different chromatic directions is influenced by the average chromaticity of the surface ensemble.
Meeting abstract presented at VSS 2015
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