Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies 304 One of its major disadvantages is expense. In the 1990s—during the advent of digital photography—several groups aimed at adapting imaging technologies to the measurement of hair luster using similar modes of analysis employed in previous goniophotometry work.4,21- 26 Overall, these imaging techniques improved the accessibility for many laboratories to be able to conduct luster measurements. Several other methods of luster analysis were also described in the literature and consist of utilizing diffuse reflectance spectrophotometry27 and a portable device capable of illuminating hair and measuring reflected light, analogous to a gloss meter.28 There has also been a considerable amount of interest in the nature of reflections of hair and how hair’s internal elements affect luster.29-31 For example, pores located in the medulla are believed to scatter light and make hair less lustrous.29 In other studies, researchers investigated the nature of the specular reflection peak, attributing small microreflections to various phenomena, including the possibility that hair cuticles may behave like diffraction gratings—separating polychromatic light into its component parts.4,25 The existence of diffraction patterns was later supported by a comprehensive theoretical treatise on the subject.5 Throughout the years, there have been several theoretical analyses of hair luster to better explain the reflection and scattering of light by hair fibers.18,32-34 Goniophotometry: Although many new techniques have appeared in the literature in the last fifteen years, goniophotometry still remains a mainstay for the measure of hair luster. A diagram of a goniophotometer is provided in Figure 3. A typical instrumental design includes a light source to illuminate the fiber(s) at a defined angle, while a detector (photomultiplier) rotates around the sample to provide a plot of reflected light intensity as a function of scattering or receptor angle. The generated plot contains both diffuse and specular components as shown in Figure 4. One experimental approach is to collect the specular and diffuse reflection together. The specular portion of the curve is then extracted by performing a Gaussian fit. As indicated by Keis et al.,