Using Garbage Masks

You can use a Mask operator to remove any part of the front image that is not keyed out. For example, if there is a prop in the blue screen, use masks to remove it from the image. In the following example, you key the dog against the clouds, then draw a mask to hide the trainer's arm.

To use a mask with the Keyer:

1. Key the front layer.
2. Select the front layer. See Making Layers the Current Object.
3. Choose Operators | Masks | Draw Mask, and draw a mask to hide any unwanted elements in the blue screen. See Image Channels.
4. In the Mask Controls panel, enable Invert for the mask object.
5. Set the Mode to Add, and continue to draw masks to hide any unkeyed elements around the subject.
6. Double-click the composite in the Workspace panel to see the result in the active viewport.



7. Play the clip to make sure the mask covers the elements for the entire duration of the clip. Animate the masks if needed. You can also track the mask to the feature that you want to hide. See Keyframing in Paint, and The Tracker.