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RE: c/ Luma coefficients for DTV



Charles,

I agree with you up to an extent. The different luma values in SMPTE 240M
were to eliminate a problem with the original formula as I remember. Also
the break point where gamma starts has been defined in 240M (.018
millivolts) where as in the old NTSC the gamma at zero was infinte and
impossible to acheive. The 240M values are correct.

What I'd like to see is getting ride of the Y'CrCb idea in production and
use only full bandwidth RGB, then these problems of Luma and color
saturation as well as "Constant Luminance" problems dissappear. But with
clients who want to have the telecine change everything (Primary's,
secondary's, saturation, etc.) I don't think going to straight RGB will
happen. Scientific accuracy is not the goal here but to satisfy the client
with pleasing pictures.

Jim Mendrala
Real Image Technology, Inc.
          

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