On Sun, 27 Jan 2008 22:00:03 +0100, Terje J. Hanssen <[EMAIL PROTECTED]>
wrote:
RGB-Float
This allocates a 32 bit float for the R, G, and B channels and no alpha.
This is used for high dynamic range processing with no transparency.
Years of working with high dynamic range footage have shown floating
point RGB to be the best format for high dynamic range. RGB float does
not destroy information when used with YUV source footage and also
supports brightness above 100%. Be aware that some effects, like
Histogram, still clip above 100% when in floating point.
...
What is really "high dynamic range processing" as mentioned above?
Using colour spaces and image formats that have a wider tonal range
than the usual 8 bits per channel. Until recently, a 0-255 brightness
scale was fine enough for most video cameras. But film has always had
a much better tonal resolution than that. Therefore the so-called
"digital intermediates" used for editing movies originated on film
use more bits per colour (like Cineon or DPX, supported by CinePaint).
Some high-end video cameras also support larger dynamic ranges, which
offer extra exposure lattitude, and better data for the colourists
and graders to work on in post-production.
Newer applications of HDR exist in computer graphics. Even though
there are no displays, film or screen, which can reproduce the
tremendous tonal range of an OpenEXR image, the actual brightness
of e.g. the Sun is useful for the generation of synthetic images.
One application of HDR is "image based lighting", described in
great detail by Paul Devebec: http://www.debevec.org/
http://en.wikipedia.org/wiki/High_dynamic_range_imaging
http://en.wikipedia.org/wiki/CinePaint
http://en.wikipedia.org/wiki/Cineon
http://en.wikipedia.org/wiki/DPX
http://en.wikipedia.org/wiki/OpenEXR
--
Herman Robak
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