Tektronix Grass Valley 3000 - Manual (Page 123)

3-15
Super Black
Super Black
Super Black is a video level that is lower than the usual black level
(7.5 IRE in NTSC; 0 IRE in PAL and Component video). It is
inserted into the background of a video signal to improve the
contrast for luminance self keying. The Super Black level is
variable 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 may be used.
The main reason for using Super Black is to enable the video,
including regular black, to be separated by a keyers’ 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.
A typical use of Super Black is when a prerecorded element such
as a flying logo is to be keyed in at the opening of a show. The
flying logo is keyed over super black and recorded on tape. (The
VTR must be adjusted to record the super black level and to
reproduce it during playback). When the logo is to be used at the
start of the show, the tape is played and the luminance key clip
and gain are adjusted to key the logo into the background scene.
The key is then activated and the tape played back to produce the
flying logo.
Refer to the Super Black text in the Appendix section of this
manual for information on how to generate and use the Super
Black output.