Keying

Keying is the process of taking a certain aspect of a video and "keying it out" (removing) it from the footage. Usually this is done to create transparent segments of the video of which other layers can be placed underneath.

The most common usage of this is the "green screen", where the color green (or blue) will be made transparent. This is commonly done in movies by having a green room the actors will work in; then the background is edited in. Just like in movies, this idea is applied to Tennis to either remove aspects of a video, or (when working with editors that cannot support alpha channels) key out backgrounds for puzzle pieces to be used properly.

Usage

All types of keying follow the same general idea:

• Choose the color that you want to key.
• Set the "smoothness" (how rough the keyed-out area is) and the "tolerance" (if similar colors should be keyed out as well).
• The keyed out area should be now transparent. Now, if you place this footage on top of another piece of footage, the bottom layer will appear underneath!

Types of Keys

Chroma Key

A chroma key (more often spelled as chromakey) is keying the image based on the chroma of the image. This is most famously used in movies and TV shows, for "blue/green screen" effects.

Color Key

While very similar to a chromakey a color key keys based on the color rather than the chroma. This is more common for computer graphics rather than movies/film.

Luma Key

Just like all the others, the luma key keys based on the luma of the image.