Color constancy refers to the fact that the perceived colors of objects remain the same even when the light reaching the eye from the objects is altered dramatically due to changes in the illuminant. The proposed research will measure how color constant the human visual system is, and investigate the cues in the visual environment that it uses to achieve this constancy. The intention of the research is to examine the strategy used by the visual system to solve this difficult computational problem and to observe the way it draws subtle information from the environment about the real colors of objects. The research concerns the basic functioning of the visual system and understanding normal visual function is an important step towards developing techniques to detect and correct vision problems. The research will be conducted using a specially constructed apparatus. The apparatus allows experimental control of the ambient illumination and of the surfaces in the observer's field of view. In addition, a projection system allows the observer to vary the appearance of a small test patch. Observers will adjust the appearance of the test patch until it appears achromatic (i.e. white, gray, or black) under a variety of different viewing conditions. The achromatic settings will be analyzed to determine a) how well the visual system corrects for changes in the ambient illumination, b) how the correction depends on the selection and arrangement of the other surfaces in the observers field of view, c) how the correction depends on the size of the field of view, and d) whether the correction depends on cognitive factors.
