295 Chapter 9 Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies Roger L. McMullen Ashland, Inc. Many visually perceptible phenomena are observed in hair. Such attributes arise due to the intrinsic properties of hair as well as the geometrical, three-dimensional arrangement of fibers into an assembly. For example, hair luster has an intrinsic component (the optical properties of the fiber) and an extrinsic component evolving from the alignment of fibers and their collective reflection. In this chapter we will introduce imaging techniques, mostly in the context of digital photography, which can be used in conjunction with image analysis procedures. In going about such a task, we must first discuss some introductory concepts about image analysis as well as the optical properties of hair. A significant portion of this chapter is dedicated to hair luster however, we will also discuss hair volume, measurement of fiber orientation by two-dimensional Fourier transform, hair curliness, hair color, and the analysis of eyelashes. Introduction In the past several decades, image analysis and processing has become a prominent tool within the scientific community to enhance the capture and subsequent processing of digital visual display data. Moreover, image analysis and processing are used to enhance images for visual perception as well as to perform image measurements.1 Quantitative measurements are usually preceded