Color Vision: From Genes to Perception. Karl R. Gegenfurtner and Lindsay T. Sharpe, eds. Cambridge, UK: Cambridge University Press, 1999. Pages: 492. Price: 100. 00. ISBN# 0‐521‐59053‐1.

Color Vision: From Genes to Perception. Karl R. Gegenfurtner and Lindsay T. Sharpe, eds. Cambridge, UK: Cambridge University Press, 1999. Pages: 492. Price: 100. 00. ISBN# 0-521-59053-1. This lovely book is written for professional vision scientists and their graduate students. Each chapter is written by an internationally well-respected expert on some aspect of color vision, and each chapter begins with a simple, clearly written, up-to-date introduction to a topic within the wide range of topics included in modern color vision. Many chapters go on to present work done by the authors, but this book differs from a set of reprints of journal articles in that much more background and review is included in each chapter. Although the authors leave their individual stamps on the chapters they contributed, the guiding hand of the editors can be seen in the uniformly readable style. Some of the topics are classics, such as the spectral sensitivities of the cones. Research and speculation on the absorption spectra of the cone pigments, and the spectral sensitivities of cones in vivo date back at least as far as Helmholtz’Physiological Optics in 1866. One might think that the topic would be exhausted by now. On the contrary, the study of cone pigments has enjoyed a renaissance over the last 15 years because of progress in molecular genetics, which has allowed investigators to sequence the genes that determine the visual photopigments. More work remains to be done in linking the genotype to the phenotype because variations in the genotype have lead us to re-examine the individual subject-to-subject variability that we had previously dismissed as “noise. ” The following chapters help the reader to understand the relationships between the cone sensitivities and color matching behavior, the spectral luminosity function and the physical disposition of different cone types across the retina, and the physiology of the cone response to light. Another classic problem is color constancy, which is the tendency of colored objects to retain their original color under different illuminants. Helmholtz called this “discounting the illuminant, ” and much of the modern work on the subject attempts to find out how the visual system knows what the illuminant is and how the brain discounts it. This problem is discussed by several authors in this book, but the best way to learn about color constancy is probably to start with Physics-Based Approaches to Modeling Surface Color Perception. In that chapter, Laurence T. Maloney reviews several major computational models that have been proposed to account for color constancy. All of the models are based on the physics of the visual scene as a stimulus, and all are designed to account for psychophysical data. Once you have understood the models, you may proceed to the other chapters that conclude with discussions of color constancy: a chapter by Zaidi on chromatic induction, a chapter by D'Zmura on color contrast gain control, and a chapter by Lennie on brain mechanisms of color perception. When you are done, you may want to read Maloney's chapter again. How are we doing in our understanding of color vision? Do we know as much as we want to know? Is there fundamental work left to be done, or are we to the point that only the details remain to be worked out? We can all profitably ponder the comment of Peter Lennie: “One should not really think about mechanisms of color at all (any more than one should think about mechanisms for orientation vision) …. In fact, I think that we tend to promote the wrong emphasis by talking about the cortical mechanisms of color vision—it encourages us to study color vision as an abstraction…. We ought first to ask about the chromatic attributes of mechanisms that underlie object vision. We can then go on to ask how the brain, when faced with the task of characterizing color appearance, abstracts that information from the responses of mechanisms used for object analysis. ” Perhaps he is right. Perhaps the trajectory to higher and higher levels of cortical processing has nearly run its course in the case of color vision. Perhaps we should be studying the perception of colored objects, just as those who study brightness have increasingly appreciated the importance of object perception to lightness constancy. However, it would be a shame if the study of color vision were dropped from the training of vision scientists, even if we were to decide that the subject had been completely exhausted. That is because color vision, unique among the disciplines of sensory science, is a well–worked out mathematical system. We can visualize the receptors, we know their sensitivities and how their sensitivities are determined, and we know how their responses predict color matching behavior and the detectability of lights. We are even a good way along in understanding the physiology of the intervening stages of visual information processing. The student who understands color vision, that is, the student who understands the biology and psychophysics of color matching and color discrimination, is well on his/her way to being able to articulate a clear, linear, computationally tractable, falsifiable “alternative hypothesis” to be tested against any explanation of any phenomenon in any sensory or perceptual modality. That should place color vision in a privileged position in the curricula of optometric and graduate programs in vision science. If you are interested in color vision, and you should be, this book will be invaluable. Angela M. Brown College of Optometry The Ohio State University Columbus, Ohio