[argyllcms] Re: Profile input white not mapping to output white
- From: Iliah Borg <ib@xxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 23 Nov 2012 19:43:10 -0500
Dear Ben,
> I need to expose another not-quite stop brighter in-camera, thus (almost)
> doubling the linear data
That is where RawDigger helps - select the target and make sure that your
whitest patch is close to saturation in the green channels (watch the red too
if shooting under incandescent light). When you shoot the target without
blowing background out it is just simpler. When I shoot (always using dark grey
as a background to reduce flare and colour reflexes) I make sure white patch is
completely blown out (blinks on camera LCD) and then decrease the exposure
until it is not. That is especially important if one is trying to profile from
gamma 1 data - because that helps to fill the whole dynamic range, without
stretching or extrapolation. You may still want to try excluding the black trap
from profile calculation and compare the results.
There is also a sort of two-stage approach possible, to reduce the noise. Make
a matrix profile, and follow it with Lab-to-Lab correction profile.
--
Iliah Borg
ib@xxxxxxxxxxx
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