738 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS numbers of small variations in skin colour that commonly occur, at least among Europeans. A more useful atlas, which is based on the Munsell system, is the Medical Colour Standard for Skin, (produced by the Japan Colour Research Institute, Tokyo). This consists of a set of over 500 colour chips mounted on strips of transparent plastic, covering a limited range of hues and having the chips more closely spaced for saturation and lightness than in the Munsell system. The disadvantages of differences in surface texture of the chips compared •vith skin, and possible deterioration with age, still remain. An alternative method of using colour standards is to prepare a set of neutral grey standards and to view the skin and standards together through goggles fitted with colour filters so as to eliminate any colour differences between the skin and the grey scale. The reflectances of the standards forming the grey scale can be easily measured by a densitometer. Pfleiderer (17) used a red glass filter in his goggles when measuring changes in skin pigmentation and a narro•v band green filter to determine the amount of erythema present. A similar system was set up independently by the author except that an Ilford monochromatic vision filter {MV 812) was used in the goggles. This filter eliminates colour differences between objects, leaving only differences in brightness, and is particularly useful when measuring changes in skin pigmentation, where no colour change occurs. The instru- ment in use is shown in Fig. 8. The standards are prepared photographically and several sets with small differences between adjacent patches can be easily constructed. The advantages of this device are the absence of pressure on the skin, ease of use, portability, and the fact that the angle of viewing can be altered to eliminate any specular reflection. It is not particularly durable, but can be readily replaced. This device is also free from un- detected errors in positioning on the skin which are liable to affect the accuracy of readings made with photoelectric instruments. Because the filters have low transmission, the level of illumination must be sufficiently high to enable the observer to distinguish the grey patches easily. Apart from this, the nature and level of illumination is not critical. PHOTOGRAPHY Photography appears to have great potential as a means of recording and measuring changes in skin colour, but so far this potential does not seem to have been fulfilled. The main problems that arise in setting up

Figure 8 Grey standard scale and goggles in use. Facing page 738