Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies 314 close the gap between real, perceived luster and image analysis- based techniques. 8. Is there anything to be gained by utilizing near-IR photography in the analysis of luster? Hair Volume Relationship between volume and body: Hair body is one of the most important attributes for the hair care consumer. It is a complex phenomenon that describes the three-dimensional state of one’s hair style and often alludes to the overall mechanical properties of the hair fiber assembly. Several single fiber properties are thought to be responsible for hair body and include curvature, friction, stiffness, diameter, cohesion, or weight of the individual fibers that comprise the hair fiber assembly.37-39 Based on consumer research in conjunction with principal component analysis (a statistical technique), it was found that three words, together, describe body: volume (bulk, thickness), springiness (bounce), and stiffness (of the hair-set, not soft).40 Other studies have emphasized the structural strength and resiliency of a hair mass as the predominant characteristics responsible for consumer-perceivable body.41 These studies were followed by the development of techniques to evaluate hair body based on the amount of work required to pull a hair tress through a specially designed template or utilizing a radial compressibility apparatus.42-45 Hair volume is recognized as a key component of hair body, and several attempts have been made to measure the three-dimensional volume of a hair-fiber assembly.46,47 Techniques to measure hair volume are becoming increasingly popular as a metric for both volume and body.48 Such methods of analysis offer the possibility to demonstrate how physical properties of the hair fiber assembly influence the volume. Three-dimensional laser stereometry: The volume of a hair fiber assembly can be measured with great facility using a three- dimensional laser stereometer. Such a device can be constructed utilizing an x-y two-dimensional translational stage and a laser