• Adobe After Effects

  Using mattes correctly to key out only part of footage?

  Posted by Matthew Chapman on January 15, 2013 at 12:32 am

  Hey there-
  I have a composition (below) which has a top layer animation with some time bend on it.

  I want to Key out the RED that is inside the melting bird, and replace it with a psychedelic pattern behind it.

  here’s the rub… I don’t want keylight to affect the background layer. I think I do this with a matte, duplicating the layer, and having the key come through just the red parts.

  If I make it one composition then apply Keying, then it affects the BG color. If I apply keying to just the top layer, then a pattern in the background shows through the whole thing (since there is an alpha on the top layer too).

  What is a good procedure for this? Anyone know?

  This is the desired effect:
  

  the file is below with a low-res BG…

  5227_birdmeltcc.aep.zip

  Matthew Chapman replied 13 years, 6 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Kevin Camp

  January 15, 2013 at 12:41 am

  you are looking at making a junk matte.

  i think this tutorial would help you out:

  https://library.creativecow.net/articles/rabinowitz_aharon/junk_mattes.php

  Kevin Camp
  Senior Designer
  KCPQ, KMYQ & KRCW
• 

  Matthew Chapman

  January 15, 2013 at 4:00 am

  Thanks Kevin, that was mostly helpful (it will certainly be helpful on other projects!). As you can see I now have a nice matt cut out from the auto trace function.

  However, I now want to use that same matte (or an inverted version of it), to ONLY allow the psychedelic BG to show through the transparency. Now as it stands, the BG takes over the whole background, per below:

  

  thanks much!
• 

  Matthew Chapman

  January 15, 2013 at 4:01 am

  Never mind, I got it working!

  Thanks guys!

  Chapman

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