Comparing Skin Colours Between Different Skin Groups

Abstract

This study investigates the basic characteristic of human skin. 47 subjects from 4 groups (Chinese, Sub-Asian, Caucasian and the Dark) were recruited. All the skin colours were measured in terms of spectral reflectance using a d:8° spectrophotometer. And they included eight parts of body locations in total: forehead, right cheek, left cheek, hand back, fist back, palm, inner forearm and outer forearm. The data revealed certain pattern for human skin colour. All the data of the four skin colour groups fit a particular curve in the $L^{*} - C_{ab}^{*}$ plane, and that is very similar to the definition of ‘Whiteness’ and ‘Blackness’ as defined by NCS, and ‘Depth’ and ‘Vividness’ as defined by Berns. The result also showed that Chinese group and Caucasian group had very similar pattern: the sunburnt part of the skin had lower Lightness value and higher Chroma value, or lower Whiteness. However, for the Dark skin group, the data show reversed pattern: sunburnt area will have lower Lightness value and lower Chroma value, and all the colours were located on the ‘Blackness’ scale. The area where the ‘Whiteness’ and ‘Blackness’ scales cross each other is the region for Sub-Asian, where they have the highest Chroma values. The difference of different skin colour groups also appears in the shape of spectral reflectance. Dark skin colour not only means lower amplitude, but also has a flatter curve shape, while for light skin colour, the spectral reflectance has a very clear ‘W’ shape. ‘W’ shape reflects the feature of human skin spectral reflectance, and that is the result of the absorption and reflection of the haemoglobin and melanin. Future work includes the study for the reason of the particular pattern shown in $L^{*} - C_{ab}^{*}$ plane and its application in various areas.