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2007.10.23 07:09 "Floating-point 32bit sample data", by Nikita V Borodikhin
2007.10.23 16:48 "Re: Floating-point 32bit sample data", by Kai-uwe Behrmann
2007.10.23 17:21 "Re: Floating-point 32bit sample data", by Joris Van Damme
2007.10.23 21:02 "Re: Floating-point 32bit sample data", by Kai-uwe Behrmann
2007.10.23 21:38 "Re: Floating-point 32bit sample data", by Chris Cox
2007.10.24 16:47 "Re: Floating-point 32bit sample data", by William B Thompson

2007.10.23 21:38 "Re: Floating-point 32bit sample data", by Chris Cox

HDR and CIE L*a*b* really don't mix.
If you have HDR data, stick to grayscale, RGB or XYZ.

HDR data _really_ needs to be gamma 1.0, and floating point image data is
best represented as gamma 1.0.

Chris


-----Original Message-----
From: tiff-bounces@lists.maptools.org on behalf of Kai-Uwe Behrmann
Sent: Tue 10/23/2007 2:02 PM
To: Joris
Cc: libtiff - Liste
Subject: Re: [Tiff] Floating-point 32bit sample data
 
Am 23.10.07, 19:21 +0200 schrieb Joris:

> Kai-Uwe Behrmann wrote:
> > > Are floating point RGB data stored gamma corrected or linearized?
> >
> > The data is best stored in a linear matrix space, much like camera
> > RAW. OpenEXR even suggests now to use XYZ instead of RGB.
> 
> Only, there isn't a photometric value for it.
> 
> RGB, without embedded ICC profile, is mostly agreed upon to mean sRGB.
> Another
> and probably more unambigious way to store color data, even if I feel RGB
> is
> regarded sRGB by just about anyone, is CIE L*a*b*, and there's a proper
> photometric for that one and a totally unambigious scale and meaning for
> floating point CIE L*a*b* data.
 
How would you handle the different gammas in CIE*Lab for typical floating 
point HDR content? 

Of course you are right to point out, that a ICC profile is needed to 
give a meaning to the image colours.

kind regards
Kai-Uwe Behrmann
--
developing for colour management 
www.behrmann.name + www.oyranos.org + www.cinepaint.org