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Keying Edge Problems: green lines when red colors

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Diego Mellado
Keying Edge Problems: green lines when red colors
on Apr 13, 2015 at 3:52:37 pm

Dear all,
Thanks a lot in advance for your support.
I have been checking tutorials for the last couple of days, but I could not find a way to get rid of the greenish line around red colors when keying a green background. Please, check the attached image as example.



Any suggestion will be much appreciated.
Best regards,
Diego Mellado.


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Dave LaRonde
Re: Keying Edge Problems: green lines when red colors
on Apr 13, 2015 at 11:50:24 pm

I'm going to guess this video was shot on a DSLR. The reason: the very bad codec to which DSLR video is recorded. It doesn't treat colors nicely. It blurs them. A DSLR's bad color is good enough to fool the human eye, but not a computer.

What you are seeing is a sharp edge between the red shirt and the green screen. If you look closely, you'll notice that it isn't a green line, it's a yellow line. Red + green = yellow.

You may have to use Rotobrush to get rid of the yellow line.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Diego Mellado
Re: Keying Edge Problems: green lines when red colors
on Apr 14, 2015 at 8:53:11 am

Thanks a lot Dave.
It was shot with a 5D MKII, but not in raw mode, so maybe the codec was an issue.
It could be yellow, yep. Any way to soften it withoout rotobrushing?
best,
Diego


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Dave LaRonde
Re: Keying Edge Problems: green lines when red colors
on Apr 14, 2015 at 4:59:50 pm

Oh, yes, the codec was indeed the issue. It's H.264. It's horrible for effects work. DSLR's stink for chroma keying.

You could use a second instance of keylight, setting it to the color of the edge.

You could create two layers, one with an animated mask around the red, apply a choker, and use the invert of the mask on the other layer to remove the red. If you don't animate the mask, the rest of the subject will look unnatural with all the choking.


In any case, you'll probably end up using multiple layers and masks.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Diego Mellado
Re: Keying Edge Problems: green lines when red colors
on Apr 15, 2015 at 7:53:56 am

Thanks a lot for sharing you knowledge, Dave.
I guess I am learnign the hard way!
Best,
Diego


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