[rescue] Re: SGI Onyx4 - uses ATI graphics chips (sigh)

Sandwich Maker adh at an.bradford.ma.us
Fri Aug 15 12:12:05 CDT 2003

"From: "Joshua D. Boyd" <jdboyd at celestrion.net>
"On Fri, Aug 15, 2003 at 08:31:23AM -0400, Sandwich Maker wrote:
"> i don't understand why the film industry would care - i'm not sure
"> it's possible to distinguish more than 30 bits of color resolution,
"> maybe even 24.
"First, when they say it is rendering 32bits to the frame buffer, I'm
"fairly certain that they mean 8 bits per channel, not two channels of 11
"bits and one chanel of 10.  In this case, 24bit and 32bit don't change
"how the picture looks, they just change how it is stored and processed.
"The extra 8 bits might be an alpha channel, or it might just be padding
"for word alignment.  In the case of SGI, I'd think alpha channel.
"Further, when you start compositing images, you need more bits to keep
"from having trouble, particularly with clipping.  One can get away with
"these bits being used for processing only, not display, but that isn't
"exactly optimal.   But most, if not all, of Windows and Linux and MacOS
"X compositing programs have to dither down to 8 bit linear graphics from
"10 log, 16 linear, 32bit float, or any number of other internal formats.

okay, that explains why you need to store the image at 16b/color
during the creation/editing phase, very well.

i'm still not clear on why even a very well trained and astute
editor's display would need to have that raw power.  surely editing
tools would be needed to zoom in on the subtleties anyway?
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought

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