two short questions alpha tips

#1
  1. What’s the best way to combine multiple alpha mattes generated by two or more keyers?

I have tried combining them in a composite with layers set to screen, add…
but it isn’t very effective to work like that, I am looking for a more flexible method.

  1. How to apply a operator to the layers alpha channel only?

I know the matte controls and alpha levels - works great.
What I mean is to apply a median filter to the matte only.
I have tried the channel selection set to “alpha”, with that method you get a selection based on the alpha channel, but you are affecting RGBA with the next operator.

#2

I find that you it could give one look at in the “Compound RGB/Alpha arithmetic op” and in “Merge Op” (C4). Although to be for the Shake this tutorial it he is sufficiently elucidative

http://www.fxguide.com/fxtips-283.html

#3

thanks Vympel
I have tried the Compound stuff, it really works. I never understood those Arithmetik operators until now.

BTW nice tutorial, look like shake is better at this task and more flexible.

#4

You can make this tutorial one in the Combustion, but the denominations of the Shake this is well different of the one of the Combustion can confuse you when trying to make this tutorial one. It thinks (at least I think thus) about compound arithmetic with one channel booleans, where the channels can have other functions of the originals it.

#5

Ok I will try it in the next days.

Any idea for applying an operator to the layers alpha channel only?

#6

In this case you must “extract” the alpha channel of the image using some operators (using Compound OP for example)e to edit this alpha channel as normal image later must transform this image (grayscale) in alpha channel using for example the Set matte.

#7

Thanks again Vympel.
Now the method is clear to me. I will figure that out tomorrow.

#8

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.