Grass Valley DD35 Family v.3.1.5 - Manual (Page 78)

2. Panel Operation DD35 Production Switcher
2 – 44 Operating Instructions – Rev. 16 / 10.2001
2.7.9 CHROMA KEY ADUSTMENTS
Pressing Chr Key selects Chroma Key mode. In this mode, the key color is propor-
tionally subtracted from the key fill signal in the key color area and colored neigh-
bouring areas. The result is a cleaned key fill signal which now contains in key color
areas shadow-free black and in neighbouring areas the de-mixed foreground col-
ors.
The key control signal is also derived from the foreground signal. The key control
signal is multiplied with the background signal. The cleaned key fill signal and the
multiplied background signal are added. This method ensures that all details are
reproduced true to the original in the area of the key color.
FGD Fade The FGD Fade (foreground fade) key switches over the chroma key processing.
Now, the cleaned key fill signal and the background signal are faded in one fading
operation by the key control signal.
In the area of the key color, only chrominance is subtractively removed, luminance
is retained. However, this will impair some advantages of the DynaChrome
t
pro-
cedure (good reproduction of details and transparency).
This mode is recommendable when object edges will show unnatural, extreme
brightenings in details and transparency areas in case of too intense CLEAN-UP
adjustments, or extreme darkenings in case of too intense DENSITY adjustments.
This mode may also be selected for improving the clean-up effect. It is required for
eliminating noise and shadows and for adapting original background to key-in-
fluenced background with DVE.
For optimal adaptation of cross fadings on edges or for optimization in case of
transparencies between foreground and background, the luminance value can be
adjusted in the area of the key color.
Adjustment is made with the L-Offset control in the Key / Chroma Key menu. Dur-
ing adjustment, Key color has to be held down.
Note: Please note that Foreground Fade is enabled automatically - without
special indication - in the following modes:
•
Chroma Key Invert
•
Chroma Key with Border
•
not Self Key.
Before adjusting Chroma Key, you should try to set optimum conditions on
the picture source side to ensure low interference, for example by an evenly
lit blue wall of maximum size and low camera gain setting.
Chr Key