... reflectance factor Rx, Ry, Rz IntroductionZB-A painting colorimeter &color tester is the professional instrument to test the object of the ... hue angle h*ab;dominant wavelength λd, excited purity Pe, color difference ΔE*ab, lightness difference ΔL*, chromaticity difference Δ ... colorimetric system and CIE 1976 (L*a*b) color space and color difference formula.3. Adopted d/o illuminating--geometrical ...