Optical Inlfuence Of Ihuminants D65and A On The Evaluation Of Jadeite (Green)

277natural jadeites’ green color were measured under standard illuminant D65and standard illuminant A by Color i5spectrophotometer based on CIE1976L^*a^*b^*uniform color space. The results of distances correlation of similarity measuresbetween variables （all correlation between vectors of values were larger than0.997）showed that Color i5spectrophotometer had good stability.The dominant wave length of58samples （λ>550nm） with green color underunaided eye exceeded the range fixed by the national standard <GB/T23885-2009jadeite grading> for jadeite （green）（490⁵50nm）, so the range of dominant wavelength about green （yellowish） jadeite should be expanded in the direction of longwave in order to in correspond with practical visual effect. It would favor theevaluation of green quality of high class jadeite, if highest chroma grade （Ch₁） wereseparated to Ch₁-H（Pe≥85） and CH2-H（65≤Pe<85）. Samples’ color with highest valuegrade （V₁） almost were in green （yellowish） samples, they were the source of highclass color about jadeite （green）. The commercial value of jadeite with low valuegrade, especially gray scale lower30, decreased obviously.According to the optical color appearance and commercial value, quality gradeevaluation of samples’ color were divided to five grades:“Excellent, Very Good,Good, Fair, Poor”.“EX” and “VG” grades came from V₁-Ch₁, V₁-Ch₂, V₂-Ch₁,V₂-Ch₂and V₁-Ch₃;“P” grades came from V₃-Ch₄, V₃-Ch₅, V₄-Ch₄and V₄-Ch₅;“G”and “F” grades came from others combination.The results of distances correlation of similarity measures between cases （allcorrelation between vectors of values were larger than0.990） showed that K-Meansclustering analysis could be used to select samples’ color with metameric quality.Partial correlation stated the change of chromaticity value was the main factor causingsample’s color mismatching under illuminant A which had metameric quality under D65illuminant.The results of two related samples’ nonparametric tests showed that standardilluminants D65and A had significant influence on jadeite’ color （p=0.005）. Whengrading the color of jadeite （green）, illuminant D with5500⁷200K color temperature,which don’t accompany yellowish or reddish tone, should be recommended,especially standard illuminant D65（6504K）. Standard illuminant A can used as testlight source to analyze the metamerism of jadeites’ color.