Papers by Author: Huan Wang

Abstract: Based on CIE1976 L^*a^*b^* uniform color space, 381 jadeite-jades’ green color were measured by Color i5 spectrophotometer. By applying clustering analysis and discriminant analysis, a classifying and grading function model of jadeite-jades’ green color is tried to be established according to L^*, a^* and b^* variable factors. The results showed that jadeite-jades’ green color were divided well into six categories by K-Means clustering analysis, and ANOVA showed L^*, a^* and b^* values among various categories were significantly different (all p <0.01). The green color of Category 5 with moderate brightness and high chroma outperformed the others, followed by Category 3. The green color of Category 2 with higher brightness and chroma was appraised to be better than the deep green color of Category 3. Dark green of Category 4 and faint green of Category 6 were in the minimum level of the quality. A linear discriminant function model of the six categories of jadeite-jades’ green color was established by Fisher discriminant analysis, which had excellent performance of discriminant with the model checking accuracy of 95.80%.It is concluded that the method of color measurement used by Color i5 spectrophotometer combined with clustering analysis and discriminant analysis offers an efficient, reasonable and feasible approach to the fast classifying and quality grading evaluation of jadeite-jades’ green color.

Abstract: Under A, CWF, D55, D65, D75 five different illuminants, color differences of 53 natural oval Jadeite-jade with fine texture are analyzed, which color is yellow-green to dark green. All 5 tested lighting sources were compared based on the uniform color space CIE 1976L*a*b*. Jadeite-jade’s lightness L* is increasing when color temperatures of five different standard illuminants increase, and it can reach the very top of 45.72 under D75, so it appears brighter and lighter than any other illuminants and it influences the appraisal of the samples’ color. The spectrum power distribution of D75, D65 and D55 reveal the strong radiant energy in the range from 500 to 570nm, so consequently the color coordinates a*, b* and chroma C* is higher than the other two illuminants. But samples’ lightness and chroma under D55 are weaker compared to D65 and the color under D55 is dark. Meanwhile, D65 stands for the average daylight and color under D65 close to the true color of samples. Because of weakest radiant energy in the range from 500 to 540nm (green area) and strongest radiant energy in the range from 540 to 570nm (orange area) in CWF’s spectrum power distribution, the absolute value of a*=14.01 is lowest and b*=12.93 is highest under CWF, so samples’ color under CWF is green with a yellow tint. The maximum hue angle h0 is 150.42 under A, and the absolute value of a* is higher than that under CWF, so it shows stronger green tone than CWF. It is concluded that D65 is preferred to be ideal illuminants for the evaluation of jadeite-jade color green especially compared with other 4 illuminants.