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How to use Matte Choker with Screen Matte
Is it possible to use the matte choker with Keylight set to “screen matte”?
Matte choker really adds a sharpness to our keys.
The reason I want to use the Screen Matte setting in Keylight is that we use it to generate a Luma channel, then use a Luma track matte on the (duplicated) layer below to create our keys. This method of duplicating a keyed shot, making a luma matte on the layer above, and then luma track matting the layer below gives us smoother keys in keylight (which seems to cause random noise and blockiness in our shots)
So, back to the original, how do I get Matte Choker to choke the screen matte in keylight? From my research it appears that the screen matte option does not create any kind of alpha, just a luma image, and matte choker needs a true alpha to work with. How do I go from Luma to alpha so that I can then choke it?
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1 Reply
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you can precomp the matte and fill, then apply matte choker to the precomp.
i think you can also tighten the key within keylight (on your matte layer).
another option would be to add unmult or xmult to ‘key’ the black out of the matte layer, then use matte choker. you would need to set the fill layer to use the alpha matte rather than luma matte of the matte layer…
also, if you haven’t already, you might want to search the cow for ‘keylight’ and ‘noise’ or ‘grain’. there have been many posts about dealing with the symptoms you are describing, and some of the solutions may help you further (although i think some decribe doing what you are already doing).
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
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