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Keying made more difficult by... (chromatic abberation? spill? what is this?)

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Gabriel TougasKeying made more difficult by... (chromatic abberation? spill? what is this?)
by on May 14, 2013 at 5:50:40 am

Hi guys, you were a real help before and I wanted to come back and try again with another conundrum.

I think I saw Dave say somewhere that keying isn't an intuitive process. You have to know how things work. And I've read the Keylight Manual cover-to-cover, but the really helpful stuff I've learned has come from Andrew Kramer's work.

What you see here is the technique that I borrowed from him : a spill-suppressed layer (using a pre-comped instance of keylight with Channel Combiner and colour-transferred onto the layer underneath) that borrows its Alpha from another instance of keylight.

This is definitely nothing new to most of you, but I thought it would be a good idea to go through the full motion when explaining it.

Anyways, the technique has been amazing to suppress colour, but that's not why I'm here.

This is the key that I've pulled on this shot. (Disregard the tracking markers, I haven't masked those yet.) Fairly satisfied with it, but I know that it could be better, because...

... this dude quite a few hairs that have been lost (this is the spill-suppressed layer).

And this is why... I'm not sure if this is chromatic aberration or spill or something else, but he's got a great deal of green in his hair.

This is what happens when I unclip my blacks and dial down the screen gain:

As you can see, the hair disappears first for some reason. It seems to go even before the screen does. It's maddening.

I have a feeling that the solution might reside in a luma key. I tried a few things, but like I said earlier, this isn't intuitive. And the luma key in AE5.5 doesn't seem to have enough precision to surround a hair or give it semi-opacity.

Thanks in advance for any help you may have to offer, and please excuse my exhaustiveness. ;-)

- Gabriel

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Todd KoprivaRe: Keying made more difficult by... (chromatic abberation? spill? what is this?)
by on May 14, 2013 at 3:37:57 pm

It looks to me like the auto-sharpen / auto-contrast mode in the camera was turned on, which gives ringing of the sort that I see in these images.

Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog

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