[argyllcms] Re: Profile input white not mapping to output white

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 27 Nov 2012 09:08:00 -0700

On 2012-11-27, at 8:52 AM, Gerhard Fuernkranz wrote:

> I.e. the question is: Which (absolute) XYZ color would the patch need to 
> have, in order that camera + raw converter would return non-clipped RGB of 
> [1,1,1] ?

Actually, I think the approach would be from the other end: what's the XYZ 
color that causes clipping at maximum RGB, but just barely, and causes no 
clipping at all for RGB values just a smidge less?

Again, empirically, the synthetic D50 white patch I manually added does exactly 
that:

1.000000 1.000000 1.000000 [RGB] -> Lut -> 100.000000 0.000090 -0.000032 [Lab]
0.999999 0.999999 0.999999 [RGB] -> Lut -> 99.999950 0.000090 -0.000047 [Lab]
0.999999 1.000000 1.000000 [RGB] -> Lut -> 99.999998 -0.000105 -0.000068 [Lab]
1.000000 0.999999 1.000000 [RGB] -> Lut -> 99.999939 0.000352 -0.000205 [Lab]
1.000000 1.000000 0.999999 [RGB] -> Lut -> 100.000000 0.000006 0.000164 [Lab]

That seems to me to show the maximum possible preservation of highlights 
without compromising the white point, which I should think is the exact desired 
outcome.

Cheers,

b&

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