Color Evaluation Of Sapphire Blue Based On Gemdialogue Color Comparison Charts

Through the measurement,screening and analysis of the color parameters of Gemdialogue color comparison charts,explore the feasibility of establishing a color quality evaluation system of blue sapphire based on Gemdialogue color comparison charts.Make the color evaluation of blue sapphire more quantitative and scientific,and provide a more objective and stable color grading basis for the market and appraisal centers.Based on the CIE 1976 L*a*b*uniform color space,use the X-rite SP62 portable spectrophotometer to measure the color of color cards G2B,CYAN,Blue,and P2B,which fit the initial range of hue of the Blue Sapphire of Gemdialogue color charts.The brown,black transparent masks and white opaque color mask are measured together with the color cards under the standard illuminants A,D65,and CWF.Each color sample can obtain five color parameters of L*,a*,b*,C,and h₀.Investigate the color change rule,distribution characteristics of the four color cards,the change of the color with and without color masks,and the influence of the illuminant on color.After the data analysis and colorimetric effect of the color expression of the samples obtained under different illuminant,the D65 is recommended for the color comparison and evaluation of blue sapphire.In the Gemdialogue Specular Circle,apart from the four single color cards,there are also three combined color cards-G1B*,P1B*and P3B*-can fit the color range of blue sapphire.They can be combined color by the combining of two single color cards.Moreover,rich color can be abtained by the combining of different zones of color cards,and different brightnesses through the combination of color masks.Screen the data measured under illuminant D65,refering to the color quality chart for blue sapphire given in the Gemdialogue?Manual.And divide the valid data into four parts:greenish-blue,cyan,blue,and violetish-blue.Each cover 3,5,6,and 9levels of blue sapphire in the color grading chart.According to this,perform K-Means cluster analysis on the color data of each part bySPSS 25.0,and color of the four part are divided into 3,5,6,and 9 categories respectively.The resulting category is associated with the initial color level in conjunction with the computer color simulation.The Fishery discriminant analysis is used to verify the classification results and obtain the corresponding discriminant analysis function.The classification accuracy of the each part is over 97%,and the results are highly consistent with the visual effect of computer colorimetry.Therefore,the classification results are accurate and ideal.98 blue sapphires with different hue are selected for color tests.Take the color parameters of each sample into the Fisher discriminant function,and plot the data of each sample into uniform color space.In the uniform color space,observe the consistency between the classification results and the visual observation results.And evaluate the feasibility of establishing a sapphire blue quality evaluation system based on the Gemdialogue color comparison charts.