Grass Valley DD10 part 1 - Manual (Page 48)

2.7 Keyers Diamond digital DD10
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2.7.14 NOTES TO THE USE OF ADD AND LUMINANCE KEY
The operational modes Add and Luminance Key differ in the fading procedure.
In the Luminance key mode, foreground and background are faded. In the add key
mode, the background is faded and the foreground is added to the background.
Key Fill Luminance Key
BGND
K
1 – K
Out
Key Fill
Add Key
BGND
1
1 – K
Out
When should Add Key be used?
Add key can always be used when the pattern (caption etc.) is available on a black
background or in the Split/Coupled Key mode, a separate key signal is available
which matches to the pattern (caption generator etc.) with regard to contour.
Since only the background is faded out at the place of the key signal with the exact
edge shape and the foreground signal is added to the faded background, both si-
gnals fit without error into each other in the transition area. Precondition is that the
key signal is processed with gain factor 1 which is achieved by actuating the Auto
key with Add Key or max. ccw position of the Gain control. Under the above-men-
tioned conditions, this key type leads to the best results and it should be aspired
to adequately prepare the key sources (e.g. captions on black background etc.).
Fill-Signal +[BGD x (1–Key)]
Key Signal
Fill Signal
BGD x (1–Key Signal)
Faded Background