Image Analysis Tools to Quantify Visual Properties of Hair Fiber Assemblies 308 peak so that only the portion of the peak within the dashed lines is integrated as S.26 Such an approach assumes that the far ends of the specular reflection curve, in fact, contribute to diffuse reflection. While many studies have been carried out in the last fifteen years using image analysis-based luster measurements, there has yet to be any inter-laboratory comparison of luster values obtained by one technique with another. In addition, there is still no consensus on analysis parameters to arrive at a final luster calculation. Luster parameters: Several factors contribute to the overall perception of luster. The intensity and defining limits of the specular reflection band are two major factors. A more brilliant specular band results in greater luster. Likewise, a narrower specular band provides more lustrous appearance than a wider one. Both of these aspects can be easily demonstrated by examining the effect of sebum on luster, which decreases the intensity of the specular band and increases its width.23 The diffuse reflection also plays a major role in determining the degree of hair shine, which may be directly attributed to contrast differences between the specular region and adjacent diffuse regions of hair. Higher intensity diffuse light will decrease hair luster while lower intensity diffuse light will increase contrast, resulting in greater luster. Figure 7. Plot of luminosity as a function of light reflection angle for the images in Figure 6