Keying is an easy and quick way of pulling a matte on a plate which can preserve many details, such as strands of hair, as opposed to rotoscoping.
Types of Keys.
Different keys are available for different situations. For example;
Red/Blue/Green Keyer: These allow you to adjust the alpha for pixels depending on their Red/Blue/Green values.
Red/Blue/Greenscreen: These allow you to adjust the alpha of pixels are predominantly the colour in question, as opposed to the individual R, G, Or B value of a pixel.
Luminance: This allows you to pull a matte based on the brightness value of a pixel. Good for removing a bright sky.
These are the main ones you will likely be using.
How to use.
A keyer will always pull a matte to the Alpha channel by default, so you will want to view the alpha channel in the viewer to see what you’re doing,