Sony MVS-8000X User Manual page 76

When only the background is changed
Preset color mix (changing background only)
76
Color Matte Settings
Current video
Color matte
New video
When a key is inserted
Key
When no key is selected
Key fades in
Preset color mix (transition including key)
By means of a Setup menu setting, it is possible to preserve
the key state while carrying out the color matte mix.
Key fades out
When a key is selected
as the next transition