On Sun, 22 May 2005, Graeme Gill wrote:
I also get the impression that HDR mapping (or rendering, which would
obviously include artistic and practical input such as white point
matching ("color grading") etc.) hasn't been as much studied in the context
of device independent color spaces, as it has from a device dependent
(ie. RGB) spaces. This isn't much of a surprise since the main impetus
seems to be from the computer graphics side, rather than the color science
side.
There is true HDR ("brightness of the sun" and "darkness under a
rock") and there is limited HDR. The Cineon log case should really be
though of as being "extended" dynamic range. It only supports about
1/2 the dynamic range of film so that data may be encoded using the
linear (in terms of density) part of the film characteristic.
It is best not to get hung up on the legacy Cineon log 10 bit case,
since log encoding can be done with any number of bits, and 12 or 16
bit storage is available (and starting to be used). The represented
density range is the same for 16 bits as it is for 10 bits.
The interesting thing about the motion picture workflow is that
usually the original image is scanned off of film, and then the final
result is printed on film. The film negative has different
characteristics than the film print, but they are both still film.
This is considerably different than going from a typically extended
range format and outputting for a limited range device like a computer
display, or printing on paper. In the film case, much more of the
original dynamic range needs to be preserved.
Schemes like EXR or one of Greg Ward's HDR encodings strive to
encode/preserve much more dynamic range than the film-to-film case
uses or desires.
Bob
======================================
Bob Friesenhahn
[EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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