ABSTRACT
Color keying operates in the Hue, Saturation, Value (HSV) mode and allows the operator to select a specific HSV value as the “center” basic keyed color, and then specify a tolerance range around that color. Luminance (Luma) Key: The luma key bases transparency on a selected value from the luminance (brightness) for the footage. Any values below (or above) a specified value will be transparent. Luma keying can be used with either a bright white backing or a dark backing. An additional form of keying that is worthy of mention is the spline key, which uses curves and control points to define the areas of opacity and transparency. The screen operation can be thought of as a method of overlaying a lighting effect onto another image. Technically, it’s the opposite of the multiply operation: the screen operation multiplies the inverse of the value of the two matching pixels.
