Raw White Point correction for LUT based profiles (DCP only)

Originally reported on Google Code with ID 1466

If you don’t use DNGs (which are automatically corrected), you may have problems with
tints in recovered highlights. You can use Raw White point (which is just a simple
factor if you don’t touch highlight recovery) to manually try to correct these shifts.

However, if you got a high precision LUT based profile, you are lost, because the colors
shift a bit using RAW White point correction. On ICC LUT profile this is a lot, on
DCP LUTs it’s just small.

However to make it perfect, this patch now makes the DCP LUT profiles aware of Raw
White point (when just using the linear correction factor, no HL preservation, which
is better done in Exposure anyway).

The practical difference depends on profile and camera. For a sample Canon 7D image
with increased Raw White point by 1.5, I measured an additional total throughput perceived
color error of 1% (on average, more on certain colors), which is eliminated with this
patch.

This also makes RAW White point linear correction factor a nice base brightness correction.

Reported by oduis@hotmail.com on 2012-07-06 15:43:05

Attachment: RawExpoDCPLUT.patch

Beep6581 / RawTherapee

Raw White Point correction for LUT based profiles (DCP only) #1450