[Openicc] review of new wide gamut editing space

[Chris Lilley]

On Thursday, March 22, 2012, 12:33:22 AM, James wrote:

>>>>>> "CM" == Chris Murphy <lists at colorremedies.com> writes:

CM>> If we go to 32bpc float as a minimum across the board, neither
CM>> primaries nor TRC matter at all.

JC> This segues nicely to a questing I've been pondering off and on for
JC> a bit:

JC>   Given an unconstrained 32-bit float workflow, what are the
JC>   ideal values to pass, eg, to lcms2's cmsCreateRGBProfile()?

JC> It seems reasonable to do the work in linear rgb; that simplifies
JC> specifying the tone curves.

Yes, as long as there is precision to spare then a linear space makes compositing etc work correctly.

JC> But is there any value to choosing a specific white point and set of
JC> primaries?

Given that Lab, when used as an ICC PCS, specifies D50 then there is extra work and possibly some loss of precision when using a non-D50 wp; values need to be adapted.

JC> Given sRGB's prevalence, one might suggest D65 and the sRGB primaries.

sRGB primaries are fine provided on has a linear space and values are not constrained to be positive or in gamut.

JC> Unless, perhaps, when working towards HDTV or digital cinema output, yes?

Wide-gamut HDTV uses the sRGB primaries, if I understand correctly. Digital cinema seems to use HDR with Absolute XYZ



-- 
 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
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