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Benjamin J. Balas, Mariko Jameson, Pawan Sinha; The illusion of ‘pan-field’ color. Journal of Vision 2004;4(8):161. doi: 10.1167/4.8.161.
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It is well known that spatial acuity and cone density decrease rapidly in moving away from the fovea in the human eye. Despite this, our subjective experience is that of ‘pan-field’ focus and color. That is to say, notwithstanding the physical limitations on resolution and color sensitivity across much of the retina, we perceive the world as being both in focus and in color everywhere in our visual field. We examine here the phenomenon of pan-field color. Specifically, we test the hypothesis that a ‘filling-out’ process that extrapolates color from the center of the visual field outward might be responsible for the illusion. We presented subjects with images of natural scenes that were either in full-color, grayscale, or of ‘chimeric’ color content. ‘Chimeric’ color images could either be of normal saturation in a central region with zero saturation in the periphery, or the reverse (grayscale in the center, color outside). When asked to indicate the color content of briefly presented stimuli, we find that subjects show a significant increase in ‘full-color’ false alarms as one increases the size of a central, saturated region in a chimeric image. ‘Grayscale’ false alarms do not significantly increase if the same manipulation is carried out with monochrome-center images, suggesting that the ability to perceive color at the fringes of these stimuli is intact. Finally, when the same task is performed with 1/f noise patterns of only one hue, ‘full-color’ false alarms almost never occur in either type of chimeric image. This suggests that ‘pan-field’ color may be achieved, at least in part, by high-level processes that use rudimentary scene analysis to fill-in the color composition of natural images.
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