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Stephen Ivory, Alan Gilchrist; Black rooms seen through a veiling luminance: gradient amplitude vs highest luminance. Journal of Vision 2012;12(9):1218. doi: 10.1167/12.9.1218.
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Gilchrist and Jacobsen (1984) showed that all-black rooms appear darker than all-white rooms because the luminance gradients are steeper in the black room due to the lack of mutual illumination. Gilchrist and Ivory (2011) showed that reducing the luminance amplitude of the image by viewing the black room through a veiling luminance makes the room appear white. To compare the relative strength of gradient amplitude and highest luminance effect, a white square was added to the black room viewed through a veil. If highest luminance governs, the room will appear darker. However, if the low gradient amplitude dominates, keeping the room white, the white square should look self-luminous. Fifteen observers viewed a small 40 cm cubic room with all walls and random objects painted matte black. The white square was placed on the face of a large cube. The veil, which filled the entire aperture through which the room was seen, was created by reflecting a rear-illuminated sheet of acrylic onto a clear sheet of glass through which the room was viewed. Mean Munsell match for the room was 8.6, marginally darker (p=.06) than the room without the white square. All fifteen observers reported the white square as self-luminous and three reported seeing the veil. This suggests that gradient amplitude is more influential in determining the lightness of the room than highest luminance. In a second experiment, the white square was replaced with a white 3D object. The room appeared significantly darker (Munsell 7.1); only one observer reported the object as self-luminous; and seven observers saw the veil. This suggests that the shape-from-shading gradients in the object prevented self-luminosity, yielding darker matches for the room.
Meeting abstract presented at VSS 2012
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