Creating a garbage matte for a green screen

One of the first steps when you're dealing with green screens is to mask out the unwanted areas of your image before applying a Keyer filter to remove the green. This allows the Keyer filter to work a little less hard because it has fewer colors it needs to remove. Let's see how we can easily add a mask using the Bezier Mask tool within Motion.

Getting ready

Locate a piece of green screen footage preferably a shot with little to no camera movement. Create a Motion project that matches the resolution settings, frame rate, and duration of your clip. Make sure you are at the beginning of your project and bring the clip into the Canvas by importing it from the File Browser. Play back the clip and become familiar with your shot. The object here is to make a mask around what you want to keep. If the subject is moving, it would be best to find a frame where the action of your subject is the most extended (that is, when their hands or feet extend out from...