Foreground Correction
Previzion has separate foreground and background primary color correctors, useful for adjustments to help blend the live action into the background.
The controls are similar to a Photoshop Levels call, with gamma controls for red, green, and blue, and in/out points for the black and white levels. Clicking Reset resets the values to their default configuration, and clicking Enable enables or disables the color correction. Color correction is done after the keying process, and so does not affect the keying.
Background Correction
The background color corrector has similar controls to the foreground, with the addition of a real time screen sampling tool to find the RGB values of the composite image. This is useful when attempting to match whites and darks in the foreground to their matching colors in the background.