Application of the Entropy Method and Color Difference Formula to the Evaluation of Round Brilliant Cut Diamond Scintillation

Abstract

A modeling approach combining the entropy method and color difference formula is proposed in order to quantitatively evaluate diamond scintillation. The images of 66 diamonds were captured from 0° to 105° rotation at 15° intervals. The color difference of corresponding pixels in adjacent rotation angle images was calculated using a MatLab r2014a program, which indicated the diamond’s color change due to its scintillation. A threshold (10) was determined to divide the color difference into seven color difference intervals, the percentage of which indicated the color-change area. The color difference and the percentage were comprehensively analyzed using the entropy method to evaluate diamond scintillation objectively and quantitatively. Lightness was the main factor affecting the diamond scintillation while chroma and hue also significantly affected it.

The Effect of Munsell Neutral Value Scale on the Color of Yellow Jadeite and Comparison between AP and K-Means Clustering Color Grading Schemes

“…where ∆L , ∆C , ∆H represent the difference in lightness, chroma, and hue angle, respectively. The weight functions S L , S C , and S H are used to calibrate the uniformity of the color space, and the function R T is used to correct the deflection of the color tolerance ellipse in the blue area; the parameters K L , K C , K H are to correct the experimental conditions in gemology, where the parameter combination is usually set as (1:1:1) to provide better perceptibility [44].…”

Feasibility Study on Color Grading of Blue Iolite Based on GemDialogue Color Comparison Charts

“…In order to better ensure the accuracy of color grading of colored gemstones, the CIE1976 L*a*b* uniform color space system was introduced and played an important role in the color quantization research of gemology. It mainly involves jadeite [14], peridot [15,16], iolite [3], amethyst [17], citrine [18], chromic garnet [19][20][21][22], tourmaline [23,24], sapphire [25], chrysoberyl [26], cubic zirconia [27], blue amber [28], and diamond [29].…”

Study on the Color-Influencing Factors of Blue Iolite

“…In recent years, colorimetry has played an important role in gemology, mainly involving materials such as jadeite [12][13][14], diamond [15], sapphire [16], peridot [17,18], amethyst [19], tourmaline [20,21], chrysoberyl [22], color-changing garnet [23][24][25][26], amber [27] and cubic zirconia. However, evaluation and analysis of factors influencing iolite color have been scarce so far.…”