Description of Research Expertise

KEY WORDS:
Color vision; color constancy; vision; adaptation; image processing.

RESEARCH INTERESTS
Visual perception and its neural mechanisms; digital image processing.

RESEARCH TECHNIQUES
Psychophysics; computational modeling; fMRI.

RESEARCH SUMMARY
My primary research is concerned with human color constancy. Defined broadly, this is the question of how color appearance provides us with information about object identity. I consider color constancy an important model problem because it nicely isolates the type of ambiguity that makes perception difficult: the image confounds the spectral properties of objects with those of the illumination.

Our psychophysical work has sought to extend our understanding of human color constancy to more naturalistic stimuli than have been studied previously. Under the rich viewing conditions used in my lab color constancy is a robust and regular phenomenon, and we have developed experimental techniques to explore systematically what image features contribute to color constancy. The psychophysical research has been guided by analyses of the computational problem posed by color constancy. Our computational work has led to an effective color constancy algorithm and we are in the process of testing whether this algorithm can serve as a model for human performance. In addition, thinking about the computations the human visual system must perform to provide useful perceptual representations has led a line of research directly concerned with how to improve digital color image processing algorithms.

I would also like to understand the neural mechanisms that mediate color constancy. We have begun to use fMRI in conjunction with psychophysics to study the cortical representation of color, with the longer term aim of developing techniques that would allow us to link physiological measurements and color appearance.