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Linear key
This is a variant type of luminance key, but with reduced variability in gain.
• In a D2 system, the key source signal including the chrominance component
is used to determine the key.
• In a D1 system, the key source Y signal is used to determine the key.
Clean key
In a luminance or linear key the key source is used as a mask on both the
background (i.e. to cut the hole) and on the key fill (i.e. trimming it to fill the
hole). The clean key technique, on the other hand, does not mask the key fill,
but simply mixes it with the background from which the hole has been cut.
This tends to provide a higher quality result, but means that the key fill signal
must already be trimmed to fit the hole (i.e. black everywhere else).
Chroma key
A particular hue (usually blue) in the key source signal is used to determine
the hole to be cut in the background.
Using chroma keying requires the optional BKDS-2031 Chroma Key Board.
Option
In addition to the BKDS-2031, using chroma keying in a D2 system requires
the optional BKDS-7133 Chroma Key Analog Component Input Board.
Note
You cannot use chroma keying on the PGM/PST bank.
For details of chroma key operations, see Chapter 5.
Pattern key
This uses a wipe pattern (generated by the wipe generators on each M/E bank
and the PGM/PST bank) to cut the hole in the background and insert the key
fill. As for a wipe, you can also apply a variety of modifications depending
on the pattern, but the wipe direction and edge modifiers are not available.
Modifications to keys
There are a number of variables you can adjust to vary a key effect.
Inverting the key source
This allows a signal comprising black letters on a white background, for
example, to be used as a key source to insert the letters.
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Chapter 4 Basic Operations for Image Creation
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