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Keylight Spill Suppression

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Peter RixnerKeylight Spill Suppression
by on Feb 6, 2010 at 4:53:16 pm


I use Keylight for many years now, but today came to a old problem.

Sometimes I use multiple instances of keylight which I add to get a good Matte. I mean a luma matte. Or so to say a black and white image which I then use for the composit. But with this workflow I cannot use the excellent Spill Suppressor in Keylight.

Of course after using the matte I get heavy green spill and greenish edges. The built in Spill Supressor of After Effects helps, but it's not near the quality of the one that is inside Keylight.

So is there a way to use only the Spill Suppressor in Keylight ?
Or is there another way to fight the spill ?



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Joey ForemanRe: Keylight Spill Suppression
by on Feb 6, 2010 at 6:04:00 pm

I use the same workflow, and then just apply a Hue/Saturation effect to the base layer to suck out all the green (green channel Saturation).
You may need to adjust the Green Range sliders.
This method works well on 4:2:2 footage, less so, though often acceptably, on 4:1:1 material.

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Peter RixnerRe: Keylight Spill Suppression
by on Feb 6, 2010 at 6:49:41 pm

Hi :)

that's great, thanks. I never really saw the possibillity of single chanels in Hue/Saturation. I guess there are so many other cool things in Aftereffects, that You only find by talking about a specific problem :)

What should make the difference between 4:2:2 and other types ?

Although the color chanels are reduced and so maybe edges would be affected by desaturation, but any other method (including Keylight's) would have the same problem.

If anyone has more ideas I am still interrested.


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Joey ForemanRe: Keylight Spill Suppression
by on Feb 7, 2010 at 12:57:48 am

You know, I'm not sure whether it has to do with sort of dithering inherent in 4:1:1 compression or what, but sometimes some small portion of green in certain edges just won't go away, even after running a full range of channel desaturations. Then if it's mission critical you've got to generate an edge matte and run that through the paces.

I've just had better luck with DVCPRO footage. I think that in 4:2:2 color space the values are more purely isolated in their respective channels.

But really a lot of it also happens to do with the quality of the lighting, the lens, on-set spill reductions with gels, and subject to green-screen distance.

You might also want to try a levels adjustment to the green channel.

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Greg RobbinsRe: Keylight Spill Suppression
by on Feb 7, 2010 at 7:37:01 am

You could just apply keylight to your main footage. Don't worry about how good the key is on it and just use it for its spill features. Then trackmatte that to your matte layer (the black and white one)

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