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Chroma Keying - Green spill/reflection problem

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Rachel NelsonChroma Keying - Green spill/reflection problem
by on Aug 7, 2012 at 8:32:46 am

I'm doing some chroma keying with a green screen, using keylight and I'm having problems with the green spill/reflection on the subject's clothes.

For one, this guy is wearing white pants, and some of the green is reflected on it, so when I key it out, there's a few large holes in his pants. I've looked up tutorials on how to work around it, but none of them seem to work. I can't even get a solid white area in the combined matte or status view no matter what I try.

For another shot, it's basically the same thing, just that the green is reflected on the guy's super polished shoes instead.

Can anyone who has any suggestions or solutions to this problem help me please? Thank you very very much!


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Darby EdelenRe: Chroma Keying - Green spill/reflection problem
by on Aug 7, 2012 at 3:09:23 pm

[Rachel Nelson] "there's a few large holes in his pants."

That's happened to me before. I kept losing change out of my pockets. Had to throw the pants away and get new ones. I suppose it could've been worse though.

The only solutions I can think of would work best if you to create separate keys for the trouble areas (pants and shoes). Then you can be more specific with your keylight settings to try and retain the areas with spill.

Also the despill/alpha bias may help you. Work in the "source" view and select a color in the pants that should be solid but isn't. You'll likely have to pull this bias back a bit, which you can do by reducing the saturation of the despill/alpha bias color. I'd set the bias on the pants key and shoes key only, and set them individually for each.

Darby Edelen


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Rachel NelsonRe: Chroma Keying - Green spill/reflection problem
by on Aug 8, 2012 at 9:06:45 am

I tried your suggestions about the separate keys and the despill bias but it's still not working.. (Damn, almost wanted to buy you some new pants if they had worked)

Is there any other way to retain the spill areas besides adjusting the clip black/white & screen despot settings? I also tried using the matte choker and bringing the choke to negative, but I got other ugly black areas around my subject too.


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Darby EdelenRe: Chroma Keying - Green spill/reflection problem
by on Aug 8, 2012 at 9:02:37 pm

Can you upload a still image of your troublesome shot? Pick the most offensive still frame you can... green spill-wise anyway.

Darby Edelen


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