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Using Alexa's false colour tool?

Alexa false color

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#1 Mark Kenfield

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Posted 09 September 2013 - 07:31 AM

Hi Guys,

 

I've got my first shoot on the Alexa coming up next week, and as circumstances prevent me from being able to run exposure tests on the camera beforehand, I was wondering about using the camera's false colour feature. 

 

We'll be shooting in LogC No-Matrix, and I'm wondering what colour I'd want to see on caucasian skin?

 

Is it pink for properly-exposed Caucasian skin? Or is pink just for the highlights on caucasian skin?

 

Cheers,

Mark


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#2 Dom Jaeger

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Posted 10 September 2013 - 02:27 AM

Pink range is one stop over medium grey, a traditional rule of thumb for correctly exposing Caucasion skin (which can of course vary). Bear in mind that the false colour guide is based on the colour processing set for the particular output signal, so if the MON OUT for example is set to Rec 709, the false colour on that device will be based on a REC 709 image, rather than Log C. Not a big difference for the pink range, but definitely affects the clipping extremes.

 

Lots of this kind of information available on Arri's website:

http://www.arri.com/.../alexa_faq.html

 

or download a pocket guide user manual for the latest software version:

http://www.arri.com/...ption3_id=ALEXA


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#3 Oliver Temmler

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Posted 10 September 2013 - 03:42 AM

Correct, the camera measures whatever you set the MON OUT to show (Rec 709 or Log C). So if you are recording ARRIRAW or ProRes Log C, there is more highlight information than what is already indicated as clipping you use the false color tool with MON OUT set to Rec 709. Switch MON OUT to Log C if you want to see what's left in the highlights.

 

Please note: Film Matrix has been removed from the camera menus. So now it's always no film matrix.


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#4 Mark Kenfield

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Posted 10 September 2013 - 08:47 PM

Thanks guys, sounds like the way to go is to record LogC, but monitor in Rec709 with faces in pink for false colour.

 

I've been through the literature but am still a little confused on the exposure level for 18% Grey, do you expose it at 38% when recording in LogC or when recording in Rec709? 


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