My company works consistently with a videographer who shoots on a Canon C300 mark ii, and occasionally when we get the footage I see some green and magenta noise/artifacts that is enhanced when color correction is applied. He usually shoots in Canon Log 2 10-bit 4:2:2. Below are screen shots of a clip brought into Premiere, you can see it at the bottom right of his face by his chin and cheek. Has anyone else experienced this that has any possible solutions or knows what might be the cause of it? !
Raw footage
ALEXA_Default LogC2Rec709 LUT applied
Warm color grade applied
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Replies
I don't think 'log' is really 'raw' but who cares. I can't see from your sample pics (on laptop ) any green or magenta stuff.
I do see that the original stuff is flat ( log ) and then you apply some space to it ( alexa for some reason ) and then you apply a grade or lut to it to warm it up.. and I also note that your question is about green and magenta.
Soooooo, getting down to basics.... there are color temperatures that match film stock or white balance when shooting, no matter what you are shooting ( raw, log, rec 709, sRGB ) …. it's nice to match the color temps of light with the recording medium ( camera ). Even if people think they can get away with murder and adjust these things in post, it's a really good idea to get it right from the start.
Soooo, without going into that can of worms, cause you are already way beyond that , lets look at the samples.
A) flat ( probably about 13 stops )
B) blue ( probably your alexa lut
C) warmer ( your own adjustment )
The background ( a window to outside maybe behind talent ? ) is sunlight, typically 56K in film land. In still photo stuff it is 55K but let's just say it's close enough.
The talent is being lit by lights … you can see a spectral highlight in his eyes, you can see a shadow from his nose, and you can see FILL light on the side of his face that is NOT getting the key.
There may be an eye light in there too... to give color and beauty to his eyes. ( usually right behind camera and very soft ).
The title of question is about green and magenta,
The basic color stuff is kinda limited to blue or orange ( CTB OR CTO) and also GREEN OR MAGENTA.. what is called PLUS GREEN AND MINUS GREEN in film world.
I'm sorry but you'll have to look that stuff up.. and I suggest you google ' lee plus green', roscoe plus green, lee full cto, and lee full ctb… etc... you'll see what film crews use in giant 4-5 foot long rolls of color gels ( as well as hard gels )…
For example, if your photographer is shooting with a window behind talent he can put gels on that window ( outside so he doesn't get light kicks off it ) and balance the color and exposure ( color gels and ND gels )…
Inside, using his lights ( whatever they are ( led, tungsten, HMI, etc. ) can ALSO get gels to correct both blue/orange and green/magenta.
Here's an old color meter... used to figure this stuff out... it is set for daylight and if you look at the back there is a handy guide to help use the filters and gels and everything else so that YOU in post don't have to mess around with it....
So tell your friend the shooter to get a meter..
P.S.
thanks for the post...cause I put a 9v battery into meter I haven't used in a couple years.. and turned it on to daylight setting...and the battery immediately died... so you helped me realize I need a new battery !!
Just found something useful..
There's a free pdf file called 'davinci 15 color grading'....and on page 89, 90 there's mention of certain skin types prone to reflecting green and magenta under certain light ...
soooo, check out the solution and see if you can find some similar 'control' using Lumetri … it should be possible...
I think it's a 'tint' control to lower red a little bit ??? You'll see...
good luck !
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