Grass Valley 1200 Operation Manual - Manual (Page 25)

2-7
Concepts You’ll Need to Know
Using the Keyer menu, the clip and gain controls can be changed
to control foreground clip and background clip. In that case, the
controls independently adjust the transition edges of the
foreground fill video and the background video.
Linear Key
A linear key is similar to a luminance key except that the gain of the
key is set to a value of one (also called “unity”) so that the edges
of anti-aliased key sources are faithfully reproduced. Anti-aliased
sources, such as the output of a character generator or graphics
system, have soft edges that produce a mix between the fill and
the background at the key edge. A linear key preserves this edge.
Figure 2-3. Luminance Key Example
GVG
News
GVG
News
Key Source
Fill Video
Background with Key and Fill Inserted