[argyllcms] Re: Profile input white not mapping to output white
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 23 Nov 2012 15:19:16 -0700
On 2012-11-23, at 1:12 PM, Iliah Borg wrote:
> It has to do with both, and more with raw processing and the way you shoot
> than with anything else. But you are not listening.
Well, what's got me confused is two-fold.
First, the TIFF that I'm feeding to Argyll has no weird color shifts and looks
like a typical linear raw camera file -- confirmed by the samples in the .ti3
and by tagging the linear output with something like sRGB.
Second, the profile works very well for the chart itself, including the
lightest and darkest patches. Running profcheck gives this:
[9.578221] I13: 0.005281 0.004926 0.004770 -> 3.851130 7.556675 -4.587199
should be 0.077060 0.022064 -0.034357
[3.318288] N18: 0.530850 0.539870 0.522690 -> 96.132563 0.082416 0.822188
should be 99.354158 -0.236898 0.093899
So, what's got me utterly confused is how the profile can go from R=135 G=138
B=133 => L=96 a=0 b=1 (and a very well-behaved response below that) to
R=G=B=255 => L=97 a=108 b=-51.
What could possibly account for that *very* hard turn in the profile after
L=96, *especially* when everything below that is so close to perfect?
It just doesn't make sense to me. What's causing Argyll to extrapolate that,
though it left off almost perfectly on the neutral axis with L=96 and almost
perfectly balanced channels, and lacking anything beyond that, that that it
should suddenly make everything whiter than that not white but cyan?
It seems to me that, if you were going to manufacture input data that you would
expect to result in a straightforward input profile, you'd manufacture pretty
much the data that's in that .ti3. So where's the difference between my .ti3
and a non-screwed-up-.ti3? Which patches are leading Argyll astray?
Cheers,
b&
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