Grass Valley 1200 Operation Manual - Manual (Page 69)

3-23
Keyer
Gain and Clip
The (GAIN) control sets keyer response at the key edges. Setting
(GAIN)
low yields a more linear response to the key source,
preserving gradual or anti-aliased key edge transitions. Setting it
high increases key gain, producing sharp key edges.
The (CLIP) control sets the threshold of keyer response to the key
source. Only those areas of the source that have a higher
luminance level than the clip threshold can cut a key hole in the
background and cause foreground fill video to appear. All areas
of the source below the clip threshold will not cut a hole, and
background video will remain visible.
In the Keyer menu, (CLIP) and (GAIN) can be assigned to operate as
(FGD CLIP)
and (BKGD CLIP) controls, providing independent
foreground and background thresholds, which results in finer
edge control (Figure 3-10). The (CLIP) control sets a foreground
clip level so that any part of the key source with a luminance level
above that threshold will cause foreground fill video to appear in
the key effect. The (GAIN) control sets a background clip level so
that any part of the key source with a luminance level below this
lower threshold will cause background video to appear.
Figure 3-10. Foreground Clip/Background Clip Operation
Fgd Clip
Bkgd Clip
Edge Transition
Foreground
Background
Key Source