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Re: keying out soft subjects

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Barend Onneweer
Re: keying out soft subjects
on Jul 29, 2012 at 7:10:58 am

First: denoise the footage. Even if the noise isn't very apparent in the source material, keying will indeed bring out the noise - especially in semi-transparent areas.

If you use Keylight: set the output to 'intermediate' and not final (in the dropdown menu in the top). Keylight's built-in spill suppressor has a tendency to amplify noise a lot.

You may have less noise now - but more spill. So you use other ways of spill suppression. Playing with the Hue/Saturation filter is a good start, swinging the greens to another hue a little, or desaturating.

If you have Key Correct Pro, there's a useful spill killer in there.

And finally if that doesn't fix it I've got a bit of a convoluted trick:

Add a solid behind your greenscreen layer, in the complementary colour to the green. That means an orange-ish tint.

You should see that the green spill in semi-transparencies is now neutralized to a certain extent, but of course you don't have a transparent background.

So: you duplicate the greenscreen layer including all the keying plugins and you set the top layer blend mode to 'stencil alpha', which will force it's alpha to all layers below.

The blending of the orange solid around the edges should do a useful job reducing spill, but you can also reduce the layer transparency to reduce the influence.

To put the result on your background, you'll need to drag this comp into a new one and do the final composite in a separate comp. You may want to tweak the coloured solid a little depending on the colour of the background.

And finally, adding Light Wrap will top things off. If you don't have Key Correct Pro there are some tutorials around that will show you how to build your own.

Hope that helps.

Barend

Raamw3rk - independent colourist and visual effects artist


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