On 11/28/2016 6:59 PM, clipka wrote:
> Am 29.11.2016 um 00:33 schrieb Mike Horvath:
>> On 11/28/2016 6:05 PM, clipka wrote:
>>>> I thought there was some tapering as the Y increases? This image
>>>> suggests that is the case.
>>>>
>>>>
http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/bajwa/images/cie_3d.gif
>>>>
>>>
>>> That's not the limit of the xyY space.
>>>
>>> That's the theoretical limit of _reflective_ colours illuminated by
>>> standard illuminant C, plotted in xyY space.
>>>
>>
>> Yes, that is fine. Not sure whether to use C or D65, though.
>>
>> https://en.wikipedia.org/wiki/Illuminant_D65
>>
>> These images on Wikipedia use D65, so I may just stick with that.
>>
>> https://en.wikipedia.org/wiki/File:Cie_Chart_with_sRGB_gamut_by_spigget.png
>> https://en.wikipedia.org/wiki/File:CIE1931xy_gamut_comparison.svg
>> https://en.wikipedia.org/wiki/File:Lab_color_space.png (I think)
>
> The first two /show/ the D65 whitepoint (or, more precisely, its xy
> coordinates), but other than that they're entirely independent of any
> whitepoint. The first image even shows various other whitepoints.
>
> As for the third image, I can't see where you got the idea that it has
> anything to do with any whitepoint (except maybe for the fact that the
> sRGB colour space, of which a few slices are shown, is defined such that
> its "upper right" corner coincides with D65).
>
> (Of course the image files themselves may also happen to be using a
> colour encoding scheme that uses D65 as its nominal whitepoint, but I
> don't think that's relevant in this context.)
>

Okay, sorry, I didn't think it was possible to compare different color 
spaces like sRGB or Adobe RGB without selecting a white point.

Still, I would like to plot the horseshoe in 3D, anyway, using a 
specific white point. (Or maybe multiple images, each with a different 
white point.)

I don't think I'll figure out the math though.

Mike

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