Metamerism Appreciation of Jadeite Jade Green under the Standard Light Sources D65, A and CWF
We tested 288 pieces of the polished cabochon jadeite jade with high quality green and smooth surfaces using the colorimeter Color i5 based on the CIE 1976 L*a*b* uniform color space. The color changes after alternating three CIE standard light sources D65, A and CWF were compared, and the degree of metamerism was evaluated. The results show that the CIE standard light sources D65, A and CWF increase the chroma of green and turn bluish green into vivid green, which are similar or to nearly colorless and transparent glass like samples with fine textures. When the three light sources were individually alternated, the lightness of the jadeite jades showed little change, but the tone changed significantly. Metamerism occurred only in 3 pairs among the 16 samples that were selected by cluster analysis for quality, and the metamerism colors were highly consistent of L*D65(43.47, 46.75) C*D65(65.20, 68.80) and ho*D65(138.10, 140.23) We can conclude that the jadeite jade green gradually turns to blue when the color temperature of the light source increases. But when considering both the light sources and the samples, D65 is more suitable to be the light source of jadeite jade green when compared with the light sources CWF and A. Compared with the CIE standard green and high chroma green, high quality jadeite jade green has a slight yellow tone, low lightness and high chroma. The special metamerism index decreased to 1 when the light source alternated among D65, A and CWF. Therefore, the color of jadeite jade green might be slightly influenced by alternating of the light sources.