Chroma Keying/Color Channel Keyer 

The Color Channel Keyer is a Chroma Keyer designed for blue- and green screens. It's easier to use than the HSV-keyer but lacks a few of the more advanced settings found in other Chroma Keyer operators. In most cases, we recommend using the HSV keyer instead.

• Key Channel - sets the chroma key color (Blue, Green, or None)
• Output- defines the type of output. The options are:
  • Foreground - output the incoming source (unprocessed)
  • Alpha - output the alpha channel only (also called the Alpha matte)
  • Suppressed - output color suppression output
  • Spill - output the spill suppression channel
  • Garbage - output the garbage matte output
  • Final - output the final Compositing Output
• Blackpoint - alpha channel black point adjustment (“PED adjustment”).
• Whitepoint - alpha channel white point adjustment (“Gain”).
• Suppression - color suppression amount.
• Spill amount - spill suppression amount
• Vibrance - pre-key color vibrance adjustment

Use the Alpha output to study the alpha channel output and for easier adjustment of black point, white point, and vibrance.

Below is an example of how the Alpha channel output can be previewed: