Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies 310 Researchers at TRI-Princeton have been conducting luster measurements for many years, first using goniophotometry and more recently with imaging techniques.35 Based on the goniophotometer technique, they extract a specular curve from a plot containing both specular and diffuse reflection. After performing the Guassian extraction, they calculate S. Then, rather than isolating diffuse reflection from specular, they utilize the combined values in their equation (S+D). Eq. 7 The width of the specular peak at half of its maximum (w 1/2 ) is determined for the sample of interest and for a reference sample (w 1/2-ref )—black polished glass. More recently, Lefaudeux et al. proposed another luster model based on data obtained from a commercial instrument utilizing an image analysis-based approach.26 This methodology separates the specular reflection into two components, S in and S out , where S in is the integrated value of the specular reflection peak in the center of the plot and adjacent regions. S out , on the other hand, is the integrated value of the area under the curve at the end regions of the luminosity plot. The diffuse reflection, D, is measured from a digital photograph obtained with crossed polarizers. Eq. 8 Overall, most of the luster parameters allow for the distinction between various treatments and to detect damaging changes to hair resulting from grooming procedures. Each parameter most certainly is different on each instrument and will depend on lighting conditions and data acquisition. This is especially true for imaging technologies, in which case each camera has a distinct CCD and optical elements as well as differences that could arise due to selected