Basic Studio Directing

Keying

Mixing to a caption doesn’t work

First let’s clarify why we need to key at all. Suppose you have a white caption on a black background. You want to superimpose this over a general view. If we try just mixing the two together, the background picture dims and the caption doesn’t fully come through.

Adding a caption to a background picture

The next logical thing to do is to add a caption to the background picture. That would be fine if all of the background picture was dark, but if you added a white caption to a bright background, you would quickly end up with an illegal signal that is way too bright.

Cutting a hole

The way we get around the problem is to cut a hole in the background picture first, then fill it with the video from the caption ...