Sony MVS-8000X System User Manual page 167

Additive mix: The background, which has been cut out with the key signal, is
combined with the unshaped foreground. This is effective for a natural-
looking composite when the scene includes glass or other translucent
objects.
Plane function
In an additive mix, the foreground is not shaped by the key signal, and
variations in the (blue) background appear in the composite image. To prevent
this, it is possible to set a particular luminance level for the background, and
any parts below this level are cut forcibly.
Composing an image by chroma keying
There are two types of composition for chroma keying: normal mix, and
additive mix.
1
In the M/E-1 >Key1 menu, select HF1 'Type.'
2
Select [Chroma] in the <Key Type> group.
It becomes possible to adjust the key density (see page 165).
3
Select [Chroma Adjust].
The Chroma Adjust menu appears.
4
Carry out auto chroma key adjustments.
Also carry out manual adjustments if necessary to obtain an optimum
chroma key image.
5
In the <Mix Mode> group, select [Normal Mix] or [Additive Mix]
depending on the desired type of chroma key composition.
When using an additive mix for chroma keying, the (typically blue)
background parts of the foreground video must be converted to black. For this,
use the color cancel function (see page 171).
Using the plane function
In an additive mix, since no key is applied to the foreground, any variations in
the (typically blue) background may appear in the composite image. To avoid
this, a particular luminance level can be set for the (blue) background, and
regions of lower luminance forcibly cut.
1
In the Chroma Adjust menu, set [Plane] on.
2
Adjust the following parameter.
Key Setting Operations Using Menus
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