Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies 296 by image processing steps, which aid in the segmentation of key features in the image that one may wish to quantify. Across many disciplines there are a variety of instrumental techniques capable of generating image data, which may be subsequently analyzed utilizing image analysis techniques. This is especially true in the medical field, which has witnessed great strides in the improvement of instrumentation used for health-related diagnostics, such as magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), and ultrasound. Imaging and image analysis techniques are utilized in many other areas as well. For example, facial recognition software used by government investigative agencies relies on powerful algorithms to process images and identify a subject. In addition, image analysis finds widespread use in microscopy, materials science, astronomy, and computer vision. In applications related to cosmetic science, image analysis has been primarily employed to quantify properties or features of human hair or skin. Other application areas may include makeup analysis, microscopic characterization of emulsions, and fingernail polish applications however, there is little published information on these topics in the current literature. A principle application of image analysis for skin is to quantify the extent of wrinkling, usually to investigate the effects of active ingredients on the skin. On the other hand, image analysis has been applied extensively to luster measurements of hair. In relation to hair fiber assemblies, textiles have also been characterized with image analysis by performing two-dimensional Fourier transforms of photographic images to examine fiber alignment and geometry, thereby serving as a quality control tool for woven fabrics.2 In this account, we will demonstrate the use of image analysis to quantify important properties of hair fiber assemblies such as luster, volume, color, and fiber alignment, as well as various optical features of hair. We also examine the geometrical configuration of eyelash assemblies, which include fiber alignment, radius of curvature, and other optical effects provided by mascara treatments.