Am 06.12.2016 um 03:13 schrieb Mike Horvath:
> I'm looking at the formulas for CIELUV color space on Wikipedia.
> 
> https://en.wikipedia.org/wiki/CIELUV
> 
> The article says, "The quantities u′n and v′n are the (u′, v′)
> chromaticity coordinates of a "specified white object" – which may be
> termed the white point – and Yn is its luminance."
> 
> I have a D65 whitepoint:
> 
>     #declare XYZWhiteReference = color <95.047,100.000,108.883>;
> 
> Which of these values is u'n, v'n and Yn?

Neither. Those three values are X, Y and Z, respectively. The formula
for converting these to u' and v' are given a few lines later in the
Wikipedia article:

    u' = (4X) / (X + 15Y + 3Z)
    v' = (9Y) / (X + 15Y + 3Z)

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