This project focuses on the effects that the spatial structure of visual scenes has on the visual system's sensitivity to spatial and temporal changes in such scenes. There is a large and diverse literature showing that luminance and colour discrimination is best for stimuli whose luminance and chromatic content is at on near the adapting level and that discrimination worsens for stimuli that differ substantially from the adapting conditions. Here we examined the nature of adaptation to chromatic textured backgrounds at different stages of the visual system. We also measure temporal contrast sensitivity for various combinations of test and surround levels for different colour directions and compare temporal contrast sensitivity in uniform tests embedded in uniform surrounds to that in variegated surrounds of equal mean luminance and chromaticity. Models proposed for colour adaptation and/or constancy have generally only considered adaptation to spatially local steady levels, or to the space average as a result of eye-movements. However, the results of our studies reveal the functioning of an additional adaptation mechanism whose effects are similar to the effects of exposure to prolonged temporal modulation.
Spehar B Zaidi Q 1997 "Surround effects on the shape of the temporal sensitivity function"Journal of the optical Society of America 14 2517-25 PDF
Zaidi Q Spehar B DeBonet J 1998 "Adaptation to textured chromatic fields" Journal of the Optical Society of America A 15 23-32 PDF
Spehar B 1999 "Contrast sensitivity in uniform and complex surrounds" Invited paper, The Optical Society of America, Annual Conference
Spehar B Zaidi Q 2000 "Crispening in luminance and colour" European Conference on Visual Perception, Groningen, 27-31 August
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