Tektronix Grass Valley 3000 - Manual (Page 176)

4-38
Section 4— Switcher Operations
4. Adjust Keyer CLIP and GAIN while observing the key
waveform by depressing SHOW KEY . CLIP has the most effect
on foreground opacity, while GAIN has most effect on
background opacity.
a. Start with both CLIP and GAIN at maximum
b. Adjust CLIP slightly making the foreground barely visible
(white if looking at SHOW KEY )
c. Adjust GAIN slightly making the background barely
opaque (black if looking at SHOW KEY )
d. Re-adjust CLIP slightly to make the foreground opaque
and the GAIN slightly to make the background opaque in
that order.
CLIP has more effect on GAIN , so adjust it first, and
readjust GAIN if CLIP is changed.
NOTES: A Chroma Key is most natural if the gain is kept low. Going
further than necessary hardens the key edge, but may be unavoidable
under certain conditions.
For this adjustment, it is better to look at the SHOW KEY signal than
the M/E output, since the Chroma Keyer background suppression has
not yet been set. An alternative procedure is to switch to MATTE FILL,
adjust to white, and select black as the background source.
5. Adjust CHROMA background suppression to eliminate the
color from the background. Too much suppression results in
the background taking on its complementary color. If a vector
monitor is available, the correct adjustment places the
background “dot” in the center of the display.
6. Adjust LUMA background suppression. Reduce the luminance
of the background to zero. If there is uneven lighting,
compromise between too much suppression and some
lightening of the keyed-in background source.