EVALUATION OF SKIN COLOR 5 Table I Means and Standard Error of Lovibond MK III and GE Spectrophotometric Measurements of Munsell Color Standards (3 x 5 in.) 10 YR 6/3 L* u* v* Lovibond 60.4 + 0.3 13.5 + 0.1 20.7 + 0.1 G.E. Spectrophotometer 61.44 16.98 25.9 10 YR 7/4 Lovibond 70.2 + 0.6 20.2 + 0.2 31.5 + 0.5 G.E. Spectrophotometer 71.41 23.78 36.42 10 YR 6/4 Lovibond 60.9 + 0.18 27.1 +_ 0.1 13.7 + 0.2 G.E. Spectrophotometer 61.69 30.27 17.50 5 YR 6/4 Lovibond 59.6 _+ 0.6 24.6 +_ 0.4 20.0 * 0.7 G.E. Spectrophotometer 61.65 28.52 25.55 5 YR 7/4 Lovibond 69.0 + 2.2 24.3 +_ 0.8 21.8 + 0.8 G.E. Spectrophotometer 71.43 28.82 26.38 7.5 YR 7/4 Lovibond 70.7 + 0.7 22.8 + 1.1 26.0 + 0.5 G.E. Spectrophotometer 71.65 26.91 30.26 This is good in view of the different geometry of measurement of these two spectrophotometers. As Table I indicates, our Lovibond flexible optic Tintometer produced a desaturated color reading compared to the Munsell G.E. and Zeiss spectrophotometers. It appeared that the deviation was roughly in the same direction of the L*, u*, v* color space for all standard colors. Therefore all Lovibond measurements, except those in Table I, were corrected with q- 1.5 q- 3.6 q- 4.6 for L*, u*, and v* respectively, being the mean color differences of the two instrumental readings. For the spectrophotometric measurements of skin color a Zeiss RFC-3 with Serial Number 96870 was used. The skin of the forearm and palm was illuminated spherically, the measuring beam was at 8 ø with the normal. The field diameter was variable over 5 mm, 15 mm and 30 mm. The skin of the cheek could not be measured with this instrument. The second sample was composed of eleven white subjects, 6 female and 5 male, and visually selected to rather extreme variance in skin color. The measurements took place in the third week of November 1979. The median and mean age of the sample were 28 and 29 respectively. The range was from 24 to 45 years old. The results are shown in Table II. A representative diagram of the differences of measurement in the L*, u*, v* color space between the Lovibond MK III and the Zeiss RFC with 30-mm field can be read from Figure 3a and b for each subject separately. We presented only the data for outer forearm because this area has approximately similar pigmentation as the facial skin.

6 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Means and Standard Deviations of Corrected Lovibond MK Ill Measurement (Values Corrected to Munsell Standards) and Zeiss RFC-3 Spectrophotometric Differences of Palm, Inner Forearm, and Outer Forearm for 11 Subjects with Increasing Field Diameter Lovibond values L* u* v* Palm 56.49 _+ 1.9 11.3 _+ 1.4 11.78 _+ 0.9 Inner forearm 62.88 + 1.9 9.72 + 1.6 16.81 + 2.4 Outer forearm 55.55 -+ 1.4 15.79 _+ 2.2 21.28 _+ 1.9 Zeiss-Lovibond differences--Zeiss at 5-mm field diameter AL* Au* Av* Palm 1.79 + 1.6 3.5 -+ 1.8 1.6 + 1.3 Inner forearm 1.07 + 0.8 2.8 _+ 1.9 1.65 + 1.7 Outer forearm 2.1 _+ 1.8 2.92 _+ 1.8 1.66 _+ 1.4 Zeiss-Lovibond differences--Zeiss at 15-mm field diameter AL* Au* Av* Palm 3.97 + 2.2 10.24 _+ 2.5 3.62 _+ 1.8 Inner forearm 3.7 -+ 1.4 8.7 _+ 1.9 4.7 + 1.7 Outer forearm 4.15 _+ 2.9 9.69 + 2.5 4.17 _+ 1.5 Zeiss-Lovibond differences--Zeiss at 30-mm field diameter AL* Au* Av* Palm 6.62 + 2.0 12.1 _+ 2.0 6.44 _+ 1.5 Inner forearm 4.60 + 1.5 11.55 + 2.4 5.18 _+ 1.6 Outer forearm 6.07 + 3.0 10.86 + 2.3 5.62 + 1.8 The differences in the measurement results between the Lovibond MK III and the Zeiss RFC-3 with 5-mm field diameter are small. The conclusion is justified that the different beam directions of the two instruments only affect the measurement results to a relatively small degree. The difference between Lovibond and Zeiss with the field diameter of 15 and 30 mm is probably due to volume reflection of light as it penetrates a turbid medium like the skin. Besides penetration, the scattering process also causes light travel parallel to the surface. This results in relative loss of light and hence a lower L*, when a small area is used. This phenomenon together with the different volume reflection coefficients of the shorter and longer wavelengths also explains the relatively larger redness-value(u*) of the spectrophotometric measurement with the largest viewing opening compared to the smallest opening. Also, absorption differences due to these pathlength differences may play a role. These effects will be further investigated. The problem of the measurement of the translucent medium was discussed by Hunter (17). He advises using an instrument with an illuminating beam of smaller diameter than the diameter of the viewing window itself. The difference between the diameters of the window and the beam should increase with depth of light penetration of the specimen. However, because of the curvature and pliability of the skin we do not recommend the use of such a large field diameter, because the skin of the palm and the