348 JOURNAL OF COSMETIC SCIENCE Table III Calculated Luster Parameters for Various Polymeric Treatments of Hair (f8 1/6 s) Treatment Peak intensity N C LReic,_Robbi• Lstam m Untreated 168 _+ 4 0.80 + 0.02 0.54 + 0.07 0.72 + 0.03 VCL/VP/DMAEMA 177 _+ 3 0.83 0.68 + 0.07 0.76 + 0.02 PVM/MA 164 + 4 0.81 0.73 + 0.03 0.80 + 0.01 IEHC 170 _+ 10 0.81 0.67 + 0.13 0.79 + 0.02 ZnO displays less tendency for whitening skin or hair, resulting in esthetically accept- able products. For demonstration, Figure 12 contains images of hair treated with various quantities of ZnO ranging from 7.5 mg ZnO/1 g of hair to 30 mg ZnO/1 g of hair. As the amount of ZnO on hair increases, the specular reflection curve becomes wider. This is evident not only in the images in Figure 12, but also in the plot of luminance as a function of tress length in Figure 13. Also shown in Figure 13 are the diffuse reflection curves (obtained with cross-polarizers) that reveal an increase in width and intensity for higher concentrations of ZnO. It is important to note that all images of the ZnO-treated hair were obtained using the exposure values f8 and 1/3 s, allowing us to accentuate areas of the hair tress outside the periphery of the specular reflection band. The luster parameters, calculated accoMing to the three different methods, are collected in Table IV. They all reveal numerical decreases with increasing ZnO concentrations, which is consistent with the visual impression of the images presented in Figure 12 and the shape of the light distribution curves shown in Figure 13. Finally, we have also examined the dulling effect on hair produced by treatment with artificial sebum. A photographic record of untreated and sebum-treated hair is shown in Figure 14. It demonstrates a significant loss in maximum light intensity as well as a broadening of the specular reflection. Quantitatively, the peak maximum light intensity was reduced from 168 + 4 for untreated hair to 127.01 + 3.56 for sebum-modified hair (Figure 15). Peak width increased from 6.71 + 0.35 to 11.39 + 0.29 for untreated and untreated 0.5g/2g lg/2g 1.5g/2g 2g/2g Figure 12. Images of hair treated with various amounts of ZnO. Exposure values: f8 and 1/3 s.

LUSTER QUANTIFICATION OF HAIR 349 250 200 150 100 50 0 -15 2g t ,Sg untreated 1 g.----• l.Sg -5 5 15 25 35 45 55 Distance (ram) untreated Figure 13. Light distribution curves for hair treated with various amounts of ZnO. 65 Table IV Luster Parameters for Hair Treated With Various Amounts of ZnO (f8 1/3 s) Amount of ZnO Peak width: W1/2 (mm) N½ Peak intensity LRei,,3_Robbi,,• Lst .... Untreated 8.30 + 0.20 0.80 + 0.02 215 + 2 0.37 + 0.02 0.67 + 0.02 0.5 g 9.55 + 0.12 0.75 204 + 4 0.31 + 0.01 0.66 + 0.02 1.0 g 9.55 + 0.51 0.71 207 + 5 0.28 + 0.03 0.62 + 0.02 1.5 g 10.41 + 0.22 0.64 211 + 1 0.24 + 0.02 0.60 + 0.03 2.0 g 11.57 + 1.25 0.65 216 + 3 0.20 + 0.03 0.56 + 0.03 sebum-treated hair, respectively. In contrast to this, luster parameters LReic3_Ro33in s and Lstam m were found to be equal to 0.34 + 0.05 and 0.74 + 0.03 for sebum-treated hair versus 0.72 + 0.03 and 0.54 + 0.07 for untreated hair, respectively. Thus, the observed dramatic loss of gloss in sebum-treated hair is not reflected in the calculated values of Lstam m. However, LReich_Robbin s coincides very well with visual observations. SUMMARY AND CONCLUSIONS An image analysis system was employed to quantify the optical and luster properties of hair. Untreated and treated hair tresses were mounted on a cylindrical support and illuminated with a collimated polarized halogen light at an incident angle of approxi- mately 30 ø relative to the horizontal optical axis. A digital camera with a resolution of 4.0 megapixels was employed as the recording device. Data, obtained in three different