Although there is generally no one-to-one correspondence between illuminants and white points, in the case of the CIE D-series standard illuminants, the spectral power distributions are mathematically derivable from the chromaticity coordinates of the corresponding white points.
12.
In reflection mode, this is often ( but not always ) taken as the of the 2?observer and standard illuminant C,, . ) Equations for " u " 2 and " v " 2 are given below:
13.
The tri-stimulus value Y gives a measure of the lightness of the material as defined in ISO 7724-2 requiring a 45?/ 0?geometry to be used with standard illuminant C and 2?observer ( although it is mentioned that slightly different conditions will not result in significant errors ).
14.
To deal with the problem of having to compare light sources of different correlated color temperatures ( CCT ), the CIE settled on using a reference black body with the same color temperature for lamps with a CCT of under 5000 K, or a phase of CIE standard illuminant D ( daylight ) otherwise.
