Friday, November 22, 2019

[Avid-L2] Working in RGB project and switching to 12 bit output shifts black up?

I'm trying to understand more about how Avid is working when it comes to the Color Space settings.  I have always worked in YCbCr 709.  I'm poking around in the various RGB project settings and I find whenever I set the Maximum Output Bit Depth to 12, which can only be done in an RGB Color Space, the image seems to suddenly scale as if a Full Scale to Legal was applied. 

I played around and made a black jpeg in photoshop and if I bring import it into the RGB 709 project and tell it to scale full range to legal the black level is elevated to approx 50 mV on the scope.  If I import with no scaling then the black is a 0 mV.  This seems logical given that an RGB project is meant fo be Full Range but what doesn't make sense is that if I leave the maximum output bit depth set to 10 bit I see none of these level shifts and black stays at 0 mV on the scope.  It's only when I toggle to 12bit that I see these shifts.

I'm on MC 2018.12.7, Mac OS 10.12.6 mid 2012 MacPro 3.46 12 core with an Avid DNxIO.

I'm not familiar with these types of projects but I just don't understand why switching maximum Output bit depth would cause level shifts.  Adding more bits shouldn't change the level should it?  It's as if by switching to 123 bit it's enabling a Full Range timeline whereas when in 10 bit Avid treats it like a legal level timeline.  I'm very confused on this.

Help me Mr. Wizard???

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net

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