... diffuse reflectance factor Rx, Ry, Rz IntroductionZB-A color difference meter is the professional instrument to test the object ... wavelength λd, excited purity Pe, color difference ΔE*ab, lightness difference ΔL*, chromaticity difference ΔC*ab, hue difference ΔH*ab, Hunter system L ... system and CIE 1976 (L*a*b) color space and color difference formula.3. Adopted d/o illuminating--geometrical viewing ...