Black Point Compensation (BPC) - another track
Black Point Compensation (BPC) - another track
- Subject: Black Point Compensation (BPC) - another track
- From: Wilma Kay <email@hidden>
- Date: Sun, 8 Feb 2009 08:50:09 -0800 (PST)
Hello ColorSync Folks,
Continuing on this black point
compensation thing, but on another track, I had a close look at two ICC v2 sRGB
profiles on the ICC's www.color.org site. These MatTRC profiles are named sRGB_IEC61966-2-1_noBPC.icc and
sRGB_IEC61966-2-1_withBPC.icc.
They fix the D65 MWP problem of the
old sRGB profile that Adobe applications aptly ignore but bring up some
questions that don't seem to be well answered by the associated ICC committee descriptions
(I think ICC folks sometimes obfuscate instead of clarify).
The ...withBPC is the same as the classic
sRGB with MWP fixed, and the ...noBPC has a TRC scaled by its MediaBlackPoint
tag.
Both profiles have a MediaBlackPoint
tag declaring a black point of XYZ = [0.0121 0.0123 0.0103], which I find
strange.. An RGB value of [0 0 0] would
get mapped to an L* of almost 11 in the PCS. If informative, it is wrong for one of them (...withBPC) and if it
demands CMM action, it is wrong for the other (...noBPC).
So if, as consensus seems to have it
from the Forum, BPC is a CMM operation, how could these sRGB source profiles
have properties related to BPC and be so named. Why would I want to have a "flare" factor added to my images
with the ..noBPC profile? How would one
actually use the …noBPC profile?
Thanks in advance,
Wilma
Pittsford, NY
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