Volume 8 Issue 1

October 2004

Appendix A: Calculating chromaticity coordinatesThe 1931 CIE (x, y) chromaticity coordinates are calculated from the spectral power distribution of the light source and the CIE colormatching functions (Figure A1). The
where p is the SPD of the light source. From X, Y and Z, the chromaticity coordinates x, y, z can be obtained as follows:
Using x, y as the coordinates, a twodimensional chromaticity diagram (the CIE 1931 color space diagram) can be plotted as shown in Figure 6. In Figure 6, the spectral locus, the purple boundary, and the blackbody locus comprise the chromaticity diagram. The blackbody locus represents the chromaticities of blackbodies having various (color) temperatures. The CIE 1976 chromaticity diagram was constructed by mathematically transforming the x, y chromaticity coordinates to u’, v’: In the u’, v’ color space, the same distance between any two points are presumed to be perceptually equal.



