Tektronix Grass Valley 3000 - Manual (Page 257)

C-1
Definition of Super Black
Super Black is a video signal that is lower than the usual black
level (7.5 IRE in NTSC; 0 IRE in PAL and Component video). The
actual level of the signal below black varies from situation to
situation and is often limited by the device that is used to record
the signal. Typically 0 IRE is used, although values as low as -5 IRE
or -10 IRE are being used.
Objective
The main reason for using super black is to enable the video,
including regular black, to be separated by a keyer’s clip and gain
circuit from the surrounding super black level. This enables a
recorded video signal which includes black to be keyed into a
scene without using a separate key signal.
Limitations
If the video is recorded over super black due to the inability to
have the key at the same time for later keying, the video should be
recorded as shaped, as there will be no shaping signal (key)
available to modify the edges. Key softness, key opacity, and any
transparent drop shadows will be lost. This signal can only be
separated from the super black level using a luminance keyer with
the key clip level set to separate the video fill (including black)
from the super black level. Super Black there requires all of the key
edges to be hard.
C Appendix C — Super Black