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J. Cosmet. Sci., 60, 111–123 (March/April 2009) 111 The shine problem in hair: Review of imaging methods and measures for luster P. D. KAPLAN, K. PARK, J. QI, and K. YANG, TRI/Princeton Synopsis There is a need for both a better understanding of the technical drivers of shiny appearance in hair and for standard methods and measures of shine. To this end, we develop standard treatment methods for changing hair shine and examine a number of image-based measurements of luster. Using psychophysical techniques to get a perceptual reference, we fi nd that available technical measures are diffi cult to use when trying to quantify the small changes in shine associated with treatment. INTRODUCTION Despite its intuitive simplicity (1,2), and years of research (2,3), the technical measure- ment of shine remains problematic (4–6). In addition to the technical challenges presented by complex illumination, heterogeneous materials, shape, and roughness, the very nature of the “shine” question can be diffi cult to describe even when the question is asked within a single restricted application. One way to illustrate the complexity of the question is to see how the question itself changes radically with context. For example, the computer graphics professional needs an answer which will enable the production of a realistic image (2), while the vision neuroscientist hunts for biologically realistic computations, essen- tially image analysis algorithms, that could possibly be similar to those taking place in the mind of an observer the coating chemist requires answers which will help in the engineer- ing of a surface that will produce, in the observer, a favorable qualitative judgment. While the shine question for each of these practitioners is related, a successful measurement for the computer graphics community may not be at all useful for the cosmetic scientist. As cosmetic scientists, we are concerned with the often subtle, optical changes produced by thin, nearly transparent layers of particles and fi lms. In this work we restrict our inter- est to the shine of straight hair. Two recent advances motivate us to undertake this work. The fi rst is an improvement in the form of a commercially available, special-purpose polarization-imaging system that should enable computation of shine without requiring much signal processing (7). Second, there is an opportunity to extend recent progress by neuroscientists on the nature of shine to hair as a specifi c substrate. We fi nd both advances to be intriguing and to advance the state of the art, but we also fi nd through the experimental results presented here, that the goal of capturing essence of shine in hair using instrumental techniques remains elusive.