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April 2005
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2005.04.26 16:33 "Re: TIFF Technote 3, draft 2", by Kai-uwe Behrmann
> I can provide a recommendation about range for viewing - but that's about all
> it is.
> 1.0 should be diffuse white in the scene, specular highlights can go over --
> this matches typical camera behavior and provides a useful image to preview
> using a trivial (1.0 -> 255, 0.0 -> 0) mapping.
>
> Converting is another story, and optimal conversions are VERY image dependent
> when dealing with HDR data.
To make floating point a more meaningful format within the tiff spec, it
would be nice to shift away from the simple 0.0 -> 1.0 mapping approach to
a real world scene reference.
Most floating point data have some kind of reference to what 1.0 means, or
simply expect the data representing some physical unit (cd/sqr meter or
the like). The stonits tag make sense with unconverted XYZ data, while XYZ
data are not covered directly by the current tiff spec. Alternatively the
range description, suggestion by Bob, can be extended to add a physical
value to the lower and upper 'normal' bounds.
The libtiff double and LogLUV sample images gives some examples.
regards
Kai-Uwe Behrmann
+ development for color management
+ imaging / panoramas
+ email: ku.b@gmx.de
+ http://www.behrmann.name