Can I use the black background of a movie clip as transparent?

Hello,

I’ve created a movie strip with some text flying around on a black background. Now I want to overlay that on another movie with some real life footage. Can I use de black background of the text as transparent so that I can see only the text flying over the base movie. I’ve tried alpha over and alpha under, placed the text strip over and below the main strip.
Thanks for any help.

You can use the Keying node in the compositor to key on the black color to create alpha transparency. The one problem is that if there are any black shadows on the text, that area will be transparent also. That’s why they use blue and green screens for FX work. Using a black screen behind someone would make it difficult to avoid keying any dark shadows on the person.

Steve S

Yup


And you’re better off using a image sequence at least for the text for many reasons. If you’re rendering just the text out, rendering directly in a video format can produce a corrupt file, you can’t pause it, and you probably lose quality when the file is encoded when rendered, and again when combined.

Image sequence doesn’t have any of those problems, you can also use high quality format such as .exr to keep high value range for further exposure or color correction, and get a proper alpha background that goes over anything without edge problems. A .png can be good enough though, which is lossless in visual range of values.