[Tig] Apple Color strange behavior

Joe Owens jpo at prestodigital.ca
Thu Aug 12 18:10:19 BST 2010


>
> Instead, I see a curve that appears to have a gamma of 1.22.
> However, when I render it out of Apple Color without any grading,  
> the line is linear again (see figure below)!
> Can anyone explain why Apple Color is adjusting the gamma on input?

Here's some really interesting math:
Rec 709 is supposed to be somewhere around gamma 2.2, but for  
purposes of argument, its what Apple COLOR is aiming for.
Apple Quicktime (up to Snow Leopard) regarded all video as "linear"  
with a gamma factor of 1.8.

Divide 2.2 by 1.8 and it comes out to:    1.22222222222  ...  
coincidence?  Its driving every COLOR operator attempting to judge  
images on their Cinema Displays (or other VGA monitor) crazy.

This might not be the exhaustive underlying reason (because COLOR has  
more than one strange behavior), but Occam says its a good  
candidate.  Do not expect Apple to comment.  The users of this  
application are your first, last, and only line of defense.



Joe Owens
Presto!Digital Colourgrade
302-9664 106 Avenue
Edmonton, Alberta T5H0N4
+1 780 421-9980
jpo at prestodigital.ca





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