[argyllcms] Re: Profile input white not mapping to output white
- From: Iliah Borg <ib@xxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 24 Nov 2012 11:54:24 -0500
Dear Ben,
On Nov 24, 2012, at 11:47 AM, Ben Goren wrote:
> On 2012-11-23, at 11:03 PM, Graeme Gill wrote:
>
>> But away from sample points
>> all that controls it is the smoothness constraints. So all it needs
>> is for there to be a slight "tilt" near the edge of the gamut, and
>> the smoothness constraint will happily go extrapolating in that
>> direction.
>
> EUREKA!
>
> Based on this, I added the following two lines to the .ti3:
>
> ZZ1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000 0.00000 0.00000
> ZZ1 96.4220 100.00 82.5210 100.00 100.00 100.00 0.00000 0.00000 0.00000
>
> And, now, as a result, it does *EXACTLY* what I was expecting it to do, just
> using colprof -v without any other arguments. No more non-white white -- and
> the DE figures reported by the check at the end of colprof were a little bit
> better, as well.
We use this in RPP, passing to colprof synthetic white and black, however we
extrapolate to supply more realistic values of deviation.
However this alone is not enough if you are profiling for gamma 1 source data
and have 2/3 of a stop underexposure.
You may also want to look at the gamut plot of your profiles, you may be up to
an unpleasant surprise.
--
Iliah Borg
ib@xxxxxxxxxxx
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