Re: [Openexr-devel] OpenEXR files with nonlinearly encoded RGB

[Kai-Uwe Behrmann]

Am 23.02.15 um 18:46 schrieb Elle Stone:
> On 02/23/2015 12:08 PM, Bob Friesenhahn wrote:
>> However, floating point TIFF and ICC do not normally go hand in hand.
>
> I'm confused by this statement. LCMS reads and writes ICC profiles
> embedded in floating point tiffs. GIMP 2.9 exports 32f tiffs with
> embedded ICC profiles and darktable recognizes the embedded ICC
> profiles, and vice versa. And so on. And so forth.
>

LCMS is just one CMM, with its prefered set of min and maximal values
for certain colour spaces. I could never find it convincing to have
CIE*L expressed in % in LCMS, the same goes for Cmyk - a printing space.
But LCMS uses these fixed value ranges from inbuild defaults. IMO, it
would make much more sense to set colour space ranges per image and not
hard coded. So, yes the Tiff spec is mostly silent about floating point
data. Thus the implementation is at the discretion of each developer.
Only one pice of information comes to mind. Greg Ward introduced at one
point the nits tag.

How are value ranges handled inside OpenEXR supporting applications? Are
there conventions. Composing a candle light scene and a sun illuminated
scene into one image appears not straight forward - maybe.