Am 12.08.2014 17:11, schrieb Cousin Ricky:

>> Also be aware that for the approach you're probably aiming at you should
>> avoid the term "hue" altogether, unless you can be sure that the actual
>> percieved hue is stable WRT the other parameters of the model. For
>> instance, while the percieved hue of a gaussian curve-based spectrum
>> will primarily depend on the wavelength of the peak, changes to the
>> width of the curve will typically also cause a slight shift in hue.
>
> I vary the saturation by raising the gray level, not by varying the width of the
> curve, so that is not an issue.  There is a slight shift in hue due to the
> unevenness of the gray curve, but the shift is pretty much imperceptible except
> for very low saturation values, where our ability to perceive differences in hue
> is pretty fuzzy anyway.  This drift is noted in the proposed documentation.

Hmmm... why do you use an uneven gray curve in the first place? (Unless 
that's your official whitepoint, in which case officially there's no 
shift in hue.)

> Peak wavelength would not be suitable, or even workable.  The purples have two
> peaks, and the oranges and reds have a plateau instead of a peak.  (This is
> based on real-life spectral curves.)  For the remaining hues, I can just about
> guarantee that the hue of the integrated curve will not match that of the peak
> wavelength.  Even if I were to match hues to a spectral wavelength (a pointless
> effort IMHO), there are no wavelengths corresponding to purples and magentas.

I was expecting a different approach.

 From what I understand now, you have precomputed spectral curves for 
"pure" colours, and you simply compute a weighted average of one of 
those precomputed colours, the whitepoint and black; so according to my 
knowledge "you /can/ be sure that the actual percieved hue is stable [in 
relation to the whitepoint] WRT the other parameters of the model" 
(emphasis added).

OTOH, you're obviously still imposing some artificial limit on the 
saturation of colours there, as even reflective colours can - at least 
in theory - be arbitrarily narrow-band (albeit at reduced brightness).

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