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Keylight Problem
Hi,
I’m trying to key some green screen footage in After Effects and export it back to Final Cut. But I’m having a problem where every time I try, it puts these huge gray/green lines around everything. I found somwhere that suggests I set the alpha channel to “straight,” and that seems to take care of most of the problem. But when the subject is moving quickly (a dramatic hand gesture or whatnot) I still get large blurry outlines rather dramatically.
I have tried keying the subject in AE and adding the background in FCP as well as adding the background while I’m keying. Either way, the results look the same. Does anyone know how to get rid of this motion blur?
Also, the resultant video is always very grainy. Will adding a remove grain filter of some sort help with that, or is that another keying issue?
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1 Reply
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As usual Dave is totally right here.
Doing the entire key in AE is highly advisable. If nothing else, it affords you way more control over the final result. No horn tootin’ or anything, but you can check out a COW tutorial I wrote on green screen color correction that outlines some keying options you’d never be able to get in FCP.
As for the source of your problem, dealing with motion blur when trying to key is a drag and is probably the culprit here. It usually results in gray mush between the fingers and other tight spaces that move. The only clean solution I’ve found is to hand-roto those elements – suck.
I always ask my DPs to avoid 24p when shooting green screen, 30p has much less motion blur and, as a result, tends to give cleaner composites.
Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com
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