Grass Valley 1200 Operation Manual - Manual (Page 188)

5-8
Section 5— Advanced Operations
Advanced Chroma Keying
Chroma Key Auto Setup typically produces an excellent chroma
key that does not require further adjustment, but in some cases
careful adjustment yields an even better key. The following
procedure explains how to adjust the Chroma Key menu controls
for an optimum chroma key.
1. Start by setting up a basic chroma key using Chroma Key
Auto Setup. The procedure for doing this is presented in
“Section 4 Basic Operations.”
2. Make fine adjustments first to the (CLIP) control and then to the
(GAIN) control. (CLIP) adjusts foreground transparency, and
(GAIN) adjusts the background shadow noise level. In some
cases increasing (BKGD LUMA SUPPRESS LEVEL) in the Chroma
Key menu helps reduce noise.
3. Examine the foreground for color splash of the background
onto the foreground. If this exists, move to the Chroma Key
Fgd Suppress menu. In that menu, turn
[FGD COLOR SUPPRESS]
ON , and then adjust the (FOREGROUND HUE SELECT ANGLE) to
achieve the greatest level of foreground color correction.
Adjusting
(SELECTIVITY) may help if set to about 15%. Some
iterative adjustment of these two controls may be necessary to
achieve best results.
4. Use the [SUPPRESS LEVEL] soft button to select LUMA . Then
adjust (FOREGROUND LUMA SUPPRESS LEVEL) for the most natural
representation of light through or reflected from the new
background.
5. If some areas where you corrected color distortion appear
gray, adjust the
(FRINGE CONTROL) soft knob to restore color to
these gray areas. Too much fringe adjustment will begin to
shift the color of the entire foreground.