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X-Y-Z values and Yxy color space

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Among the most widely used color spaces for defining and mathematically expressing these attributes are the CIE’s Yxy color space, established in 1931; the 1976 L*a*b* color space; and the L*C*h color space. Other color spaces, such as CIELUV,
Among the most widely used color spaces for defining and mathematically expressing these attributes are the CIE’s Yxy color space, established in 1931; the 1976 L*a*b* color space; and the L*C*h color space. Other color spaces, such as CIELUV, Hunter Lab, developed by Richard S. Hunter, and the Munsell color notation system, also are in use. 

Over time, color space representations have been refined to more closely correspond to the color difference perceptions of the human eye as defined by continued experimentation and statistical averaging. 

One of the earlier color space representations is the CIE 1931 X,Y chromaticity diagram (Figure 2). The diagram is used for two-dimensional graphing of color, independent of lightness. X and Y are the chromaticity coordinates calculated from the tristimulus values X-Y-Z. In this diagram, achromatic colors are toward the center, and chromaticity increases toward the edges. A colorimetrically measured red apple whose chromaticity coordinates are X = 0.4832 and Y = 0.3045 can be located in this color space at position A (the blue circle).

XYZ colorimeter

Also referred to as CIELAB, L*a*b* color space was promulgated in 1976 to adjust for one of the problems of the original Yxy color space. Equal distances on the X,Y chromaticity diagram did not correspond to equal perceived color differences. In the L*a*b* diagram, a spherical color solid, L* indicates lightness, and a* and b* are the chromaticity coordinates. Here the a* and b* indicate color directions (+a* is the red direction, -a* is the green direction). 

3NH produces high precise and stable colorimeter and spectrophotometer, which got CE, ISO 9001, ROHS, FCC, TUV, SCM certifications. Their colorimeter spectrophotometers all have CIE XYZ, CIE LAB, CIE LAB CH, etc color spaces. Some also have CIE LUV, WI &YI color space. No matter which color space people use, they all display the color and tell us color difference. 
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