Contribution of Green Jadeite-Jade's Chroma Difference Based on CIE 1976 L*a*b* Uniform Color Space

摘要

The correlations between lightness and chroma, lightness difference and color difference, chroma difference and color difference were studied to evaluate the impact of lightness on color. Based on color difference formula CIE LAB in the uniform color space CIE L*a*b* it is learnt that ΔH*ab of jadeite jade green colors has made little contribution to △E*ab. Given the fact that human eyes are relatively sensitive to the color perception of lightness difference and that lightness and chroma affect each other, lightness of jadeites has been divided into two groups: while the lightness of green is relatively low (L* ≤ 19.52), lightness and chroma have positive linear correlation (correlation coefficient L* × C* ＝ 0.971), which means the higher lightness the higher chroma and brings brighter green color; while L* ＞ 19.52, there is no one-to-one correspondence between lightness and chroma, and the highest chroma 77.64 can be reached when L* ＝ 37.63. The high partial correlation coefficients △L*ab × △E*ab = 0.974 and △C*ab × △E*ab ＝ 0.971 reveal that both △L*ab and △C*ab are not affected by the lightness of jadeite and are equally important to △E*ab. It is concluded that the quality estimation of green color of Jadeite Jade should be primarily based on lightness which is the most intuitive factor and consistent with the color perception, and then followed by the evaluation of chroma and hue.