C - Reality Keyer
Reality Keyer is a GPU accelerated, image-based color difference keyer. Before going into operational details, we will first cover how it works and what it needs to create a good key. Reality Keyer relies mainly on the information coming from the color channels of the image coming from the camera sensor(s). For every pixel, it reads red, green, and blue values. Basically, for a green screen color difference key, alpha is calculated like below:
This means that all 3 color values and their pixel to pixel (even subpixel) alignment is very important since the keyer thinks that all color components belong to the same physical spot.