PreBlur and Tuning

Some shots can be improved by softening the foreground image that is used to generate the key. The original image is then used in the composite and color corrections. The Screen PreBlur parameter is used to do this. DV footage or grainy shots may benefit from subtle use of this control.

Tuning

Keylight creates the screen matte after the screen color has been picked. You can make fine adjustments to this matte using the Gain controls. Increasing the gain controls makes the screen matte more transparent by increasing the amount of screen color showing through the matte. This tends to tint the edges the opposite of the screen color (for blue screens, edges become yellow). Decreasing the gain makes the main matte more opaque by reducing the amount of screen color showing through the matte.

The matte can be adjusted independently in the shadows, midtones, and highlights, giving more control than the clipping levels.

The level of the midtones can be adjusted too. For example, if you are working on a dark shot you may want to set the midtone level to a dark gray to make the gain controls differentiate between tones that would otherwise all be considered shadows.