30 JOURNAL OF COSMETIC SCIENCE the naked eye. Consequently, it may play a role in the perception of luster by a consumer and affect his judgment when making a hair treatment selection. In this paper, we examine the details of the specular reflection of hair by employing macro lenses, close positioning of the camera in relation to the photographed hair samples, and a high-resolution digital camera. Image analysis was employed to inves­ tigate the distribution of light intensity and the contrast between the highlights and shadows in the specular reflection area in order to derive a parameter characterizing the luster of hair. We have also employed another image analysis technique to assess the random reflection patterns produced by black, African hair, which cannot be analyzed by methods developed for straight hair of Caucasian or Oriental origin. Finally, we have also applied the same analysis technique for frizzy, very curly, and curly hair of Caucasian ongrn. EXPERIMENT AL METHODS The luster evaluation apparatus used in this study was described previously (1). An Olympus Camedia El0 digital camera with a front-element auxiliary macro lens was employed to collect images of illuminated hair, typically one tress, from a distance of S inches. Previously, we had obtained images that contained two tresses in each photo­ graph and the camera was positioned 10 inches away from the cylinder mount (1). We also utilized a 35-mm single-lens reflex (SLR) Nikon FE 2 camera equipped with an AIS 55-mm macro lens. In our previous study, we scanned the light intensity parallel to the fiber axes of a hair tress by employing image analysis software. In this work, light reflections within the specular reflection band were measured both in perpendicular and parallel directions in relation to the fiber axes. This was accomplished by using image analysis software, Sigma Scan Pro S .0. As discussed in the Results section of this report, the horizontal and vertical light intensity plots consisted of maxima and minima, which were determined by importing the data into Mathcad 2001 Professional (MathSoft Engineering & Education, Inc.) and utilizing customized programs written within the Mathcad package. In addition to this, we utilized Image Tool 2.0 (University of Texas Health Science Center, San Antonio, TX) to quantify light reflection from curly African hair. MATERIALS Luster analysis was performed on natural white, light blonde, medium blonde, dark blonde, light brown, medium brown, and dark brown hair of Caucasian origin purchased from IHI & Products, Inc. (Valhalla, NY). In addition to this, we utilized Oriental hair purchased from DeMeo Brothers (New York) and curly African hair as well as frizzy, curly, and very curly hair of Caucasian origin supplied by IHI & Products, Inc. Hair samples were precleaned with a 3% ALS solution and thoroughly rinsed prior to ex­ perimentation. Hair tresses from Caucasian and Oriental hair were obtained by gluing 3 g of fibers to 1.5 x 1.5-in. plexiglass tabs with Duco cement. The length and width of each hair tress were 10 inches and 1.25 inches, respectively. African hair was formed into small 0.5-1.0-gram tresses by tying the upper portions of fibers with a cord. A
SPECULAR REFLECTION IN HAIR 31 synthetic sebum formula was prepared as a 5% (w/w) solution in hexane, as described previously (1). RES UL TS AND DISCUSSION QUALITATIVE DESCRIPTION OF MICROREFLECTION PATTERNS Figure lA shows a typical digital image of dark brown hair taken with a macro lens at a distance of 5 inches, illustrating the complexity of the structure of the reflection band. The white outline in the photograph presented in Figure lA highlights the region of the image that is shown at a higher magnification in Figure lB. Detailed examination of the pictures presented in Figure 1 reveals a series of light dots aligned with individual fibers. It is important to note that the image shown in Figure lB is not interpolated in any way and is shown without magnification. On the contrary, the image shown in Figure lA had to be reduced from its original size in order to fit into its current format. We address this detail since one may conclude that the multiple dot-like reflection patterns in Figure lB could be attributed to pixelation of the image. In order to further alleviate this concern, we performed similar experiments with a Nikon SLR 35-mm camera equipped with a 5 5-mm micro lens. Figure 2A provides a non-digital image of hair, obtained by using 100 ASA Kodachrome film, with a field of view similar to that shown in Figure lA. An enlargement of the inset in Figure 2A results in a more detailed view, which is shown in Figure 2B. The result confirms that the dot-like texture of reflected light is not an artifact of digital imaging. For further illustration, Figure 3 contains digital photographs of a person's head in natural sunlight. The magnified view in Figure 3 is a close-up shot of the specular band located in the crown region of the subject's head. Again, a series of dots corresponding to individual fibers can be observed to pervade the entire reflection band. These photographs, obtained by using natural, solar illumination, suggest that the observed structure of reflected light in the shine apparatus is not an artifact related to the use of the halogen light source. In our previous publication, we demonstrated the dulling effect produced on hair as a result of treatment with artificial sebum (1). Figure 4B presents a corresponding close-up image obtained for hair treated in the same manner, along with untreated dark brown hair (Figure 4A). While the microreflection patterns are clearly evident in the sebum­ treated hair, the contrast between the specular reflection centers and the diffuse reflec­ tion (background) is much greater for untreated hair than for sebum-treated hair. As yet another example, natural white hair, is compared with dark brown hair in Figure 5. Similar to sebum-treated hair, micro-reflection patterns are visible for natural white hair, although the contrast between the specular reflection (dots) and the background is much greater for dark brown than for natural white hair. IMAGE ANALYSIS OF MICROREFLECTION PATTERNS In order to quantitatively characterize the microcontrast effects arising from the presence of dots (highlights) and neighboring shadows (diffuse reflection areas) in the specular reflection band of hair, we measured the light intensity as a function of distance in the horizontal direction relative to the fiber axis. This is shown pictorially and graphically in Figures 6A and 6B, in which 250 lines (represented by horizontal lines in Figure 6A)
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