Re: [Openexr-devel] Introduction and CTL/ICC question

[Brian Willoughby]

Paul Schneider <address@hidden> offered:
[  Also, although most APIs allow you to pass a 16-bit or float ramp for
[  future-proofing, I believe that almost all video cards only implement
[  an 8-bit ramp (at least in 32-bit display mode).  I don't think there's
[  any point to having a gamma ramp bigger than 8 bits when your video
[  buffer is only 8 bit.  So, you'd have to watch for quantization, as
[  well.  I could be wrong about this, though.

Drew Hess <address@hidden> replied:
[  Nvidia Quadro cards have 10-bit DACs, actually.  I believe the frame
[  buffer is still 8-bit, though.

This means that you can still have 256 distinct output levels, without the  
gamma curve producing duplicate codes (as would be the case with an 8-bit DAC). 
 
 As you probably know, an 8-bit gamma ramp would have to repeat codes to  
express the curve, while a 10-bit gamma ramp might not.  You cannot access more 
 
than 256 levels from an 8-bit framebuffer, but at least you don't suffer loss  
when mapping through gamma.

Brian Willoughby
Sound Consulting