PremierePro

Replace a static background with Difference Matte

The Difference Matte creates transparency by comparing a specified still image with a specified clip and then eliminating areas in the clip that match those in the image. This key can be used to create special effects. Depending on the clip, it’s possible to use Difference Matte to key out a static background and replace it with another still or moving image.

You can create the matte by saving a frame from a clip that shows the static background before the moving object enters the scene. For best results, neither the camera nor anything in the background should move.

The following Difference Matte settings are adjusted in the Effect Controls panel:

View
Specifies whether the Program Monitor shows the Final Output, Source Only, or Matte Only.

Difference Layer
Specifies the track to be used as the matte.

If Layer Sizes Differ
Specifies whether to center the foreground image or stretch it to fit.

Matching Tolerance
Specifies the degree to which the matte must match the foreground in order to be keyed.

Matching Softness
Specifies the degree of softness at the edges of the matte.
Note: The RGB Difference Key uses color to define transparency much as the Difference Matte uses a still image.

Blur Before Difference
Specifies the degree of blur added to the matte.

  1. Find a frame of your foreground clip that consists only of the static background. You will use this frame as a matte. Save this frame as an image file. It will appear in the Project panel.
  2. Drag the matte frame from the Project panel to a video track in the Timeline panel.
  3. Drag the clip you want to use as the background to a track in the Timeline panel above the matte frame.
  4. Place the video clip you wish to use in the foreground on a track in the Timeline panel above the background clip.
  5. (Optional) If you’re animating the Difference Matte over time, make sure that the current‑time indicator is in the position you want. Click the Toggle Animation icons  for the settings you adjust.
  6. In the Effects panel, expand the Video Effects bin and then the Keying bin.
  7. Drag the Difference Matte effect onto the foreground video clip.
  8. In the Effect Controls panel, click the triangle next to Difference Matte to expose its controls.
  9. From the Difference Layer drop-down menu, select the track that contains the matte frame.
  10. Adjust the other settings as needed to achieve the desired effect.
  11. (Optional) If you’re animating the Difference Matte, move the current‑time indicator either in the Effect Controls panel or Timeline panel and change the Image Matte settings.

    A new keyframe appears in the Effect Controls timeline when you change the settings. You can also adjust the interpolation between keyframes by editing the keyframe graph. Repeat this step as needed.