About primatte and masks

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  02 February 2005
About primatte and masks


I'm doing a bit of keying at the moment and there are a few not so good shots of which I need to extract the actors from. I put a mask to the footage that only includes the actors and a bit of extra space and then used primatte to take out the blue.

Now, this results that I have a black rectangle surrounding the mask shape (in the output of primatte that is). So, I put the same mask to primatte as well. This gets rid of the black box but now I get artifacts along the edge of the rotoshape.

I've tried to mess with the soft edge (tryuing to remove it that is) but I do not seem to get this work for some reason. Any help from you pros?
  02 February 2005
well...when green/blue screen is not that good, i follow following steps:
if it is a NTSC video, the color output is 4:1:1, i take it to finalcut pro and export it as uncompressed 8bit 4:2:2, that way get more information about blue/green along the edge...if u dont have finalcut, ignore this step

now in shake, before matting, put a blur node and blur only the b(or green), instead of default rgba, that way it will smoothout the blue edge.

then matte it, but dont put backgroun now

give a final touch with with bluring the alpha now(blur node, this time only a)

put the background with a under node

it should work now

best of luck
  02 February 2005

Hello again.

It seems I'm a bit bad with explaining things. And being a bit impatient. So, the answer to myself: Either put up constrast a great deal, multiple thousand percents like I did, or be smart and use the Inside node. That get's rid of the jagged edge on rotoshape. One more option is to invert the rotoshape and put it to Primattes garbage-matte input.

Sorry about the double posts, I put this reply to both of them just in case somebody else ever reads and ponders those things.

Edit: Thanks for the reply still. Even if I did not try it out and it seemed to answer another question about keying, my thanks about trying to help out.
  02 February 2006
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