AfterEffects

Use a hold-out matte

Use a hold-out matte (also known as a hold-back matte) to patch a scene to which a keying effect has been applied.

A hold-out matte is a masked-out portion of a duplicate of a layer that you have keyed. The duplicate is masked to include only the area of the image that contains the key color that you want to preserve as opaque. The hold-out matte is then placed directly on top of the keyed layer.

Example of using a hold-out matte 

A.
Original bluescreen image. The number’s background is also blue.

B.
After keying, the number’s background is also transparent.

C.
Hold-out matte containing the part of the image you want to remain opaque

D.
When the hold-out matte is placed on top of the keyed image, the number’s background is now opaque.

  1. Duplicate the layer containing the color screen.
    Note: Don’t change Transform properties of only one of the layers after making the duplicate; keep the layers moving together.
  2. Apply keying effects and Matte effects to the original layer to create transparency.
  3. On the duplicate layer, create masks to mask out everything in the image except the area that you want to preserve.
  4. Make sure that the copy (the hold-out matte) is positioned directly on top of the keyed layer and contains exactly the same keyframes with the same values. Then render the movie.