734 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS imposed they form grey. The values of the Lovibond filters used to match any particular test colour provide information about its three characteris- tics-hue, saturation and lightness. In the instrument itself, the sample is viewed on one half of a circular field, while the other half of the field is provided by an illuminated white surface seen through colour filters selected by the observer. The modi- fication has been more fully described elsewhere (15), but briefly it consists of illuminating the skin sample normal to the surface by means of one light guide, and collecting diffusely reflected light at an angle of 45 ø to the normal by a second guide which passes the reflected light into the instrument, where it is matched in the usual way. When a match on a surface has been recorded, the colour is specified by the values of the red, yellow and blue filters used to make the match. Table I Skin colour measurements made with modified portable Lovibond Tintometer Lovibond values , Sensory evaluo ! ation of skin Subject Site ...... I lightne s s R B Y Total 1 IF 3.2 2.7 5.3 11.2] 2 IF 3.5 2.9 5.4 11.8• 3 IF 3.6 2.7 5.7 12.0[ Fair 4 IF 3.5 2.9 5.0 11.41 5 J IF 3.S a.1 6.5 13.4 / 6 IF 3.6 3.1 6.3 13.0• Medium 7 IF 3.7 3.2 6.7 13.6/ 5 OU 4.6 3.5 7.9 16.01 Medium, 6 OU 4.5 3.2 7.8 15.5/ slightly 7 OU 4.8 3.6 8.0 16.4 tanned 8 IF 5.2 3.3 9.1 17.6 / 8 OU 6.5 3.9 11.• 22.01 Dark Lovibond values are the matching values minus the absorption due to the light guides. Subjects 1 to 7 are European, subject 8 is Indian. IF=inner forearm OU-----outer upper arm Table I gives results obtained on a number of people compared with the subjective judgement of the lightness of their skins. Where surfaces are of similar colour but differ only in lightness it is useful to add all the filter values together as a measure of lightness. Table I shows that skins classified subiectively as fair, medium and dark cover fairly narrow ranges of Lovi- bond values, and there seems to be good correlation between total Lovibond values and sensory evaluation of skin lightness.

Figure 6 Production version of flexible optic 3•intometer in use. Facing page 735