Alpha Matte not keying out video? In this tutorial, Kenan Proffitt goes through the very simple process on how to use a matte key (picture 2) to key out a video with rotoscoping. I have duplicated his exact process by using a &quot;Set Key&quot; node with the video clip plugged into the &quot;Image&quot; input and the rotoscoped matte plugged into the &quot;Alpha&quot; input. (picture 1) It's fairly straightforward. But when I do that, the result is only half-way working. The rotoscope subject is perfectly still there while the background is only sort of transparent-not 100% transparent (picture 3). Why is this happening?
The alpha channel needs to be associated to the image. Use an Alpha Convert node and choose Straight to Premultiplied.