70 60 � 50 CJ � 40 u.. 30 20 10 0 A 70 60 � 50 ! 40 LL 30 20 10 B SPECULAR REFLECTION IN HAIR 0 0 200 Luminance 200 Luminance 37 400 400 Figure 7. Example histograms displaying the frequency of appearance for (A) peak maxima and (B) peak minima that occur in one of the horizontal lines in Figure 6.

38 JOURNAL OF COSMETIC SCIENCE 1 5 0 ....-----------------------, 140 ca 120 E ·;;: ca :i E I! en 0 . !!! :::c 100 0 Peak Maxima / Peak Minima 50 100 150 200 Vertical Distance (Horizontal Line Number) Along Fiber Axes 250 Figure 8. Horizontal luminosity analysis horizontally along a hair tress. The abscissa corresponds to each horizontal line in Figure 6, while each ordinate represents the maximum value obtained from either the maxima histogram (Figure 7 A) or the minima histogram (Figure 7B). Table I Results of Maxima/Minima Analysis for Various Types of Hair Medium Light Dark Medium Light Natural Oriental brown brown blonde blonde blonde white Maximum area 13,780 15,860 19,020 20,690 24,580 26,140 46,600 Minimum area 428 4,131 7,369 10,200 12,840 17,380 40,020 Maximum - minimum 13,350 11,730 11,650 10,490 11,740 8,765 6,586 LStamm * 0.72 0.70 0.65 0.32 LReich-Robbins * 0.67 0.32 0.19 0.06 * From reference (1). from the smaller face. It has also been suggested that microreflections from hair arise due to the internal porous structure of hair typically found in medullated fibers (3 ). As a final point, it has been suggested that such light patterns observed on hair may be due to diffraction, with the cuticular structure of hair acting as a diffraction grating (termed blazed grating) (4). We are most inclined to concur with the latter explanation, since the reflection patterns we have observed typically represent a spectrum of colors analogous to that observed with a diffraction grating when white light is split into its various wavelength components.