Apple Final Cut Pro 6 - Manual (Page 1319)

534 Part III Color Correction and Video Quality Control
Working with Analog Video
If you need to output video to an analog format, make sure you understand how
digital signal levels in Final Cut Pro are translated to analog levels.
How Analog Video Signals Are Measured
Analog video is measured using IRE units. (IRE originally stood for Institute of
Radio Engineers, which has since merged into the modern IEEE organization; the
measurement is a video-specific unit of voltage.) One IRE is 7.143 millivolts, but it’s easier
to remember that an analog video signal has a range of 1 volt, which spans 140 IRE
units. Synchronization pulses, which are necessary for an analog television broadcast,
are located between –40 and 0 IRE.
PAL and Japanese NTSC systems have luma (or Y´) values between 0 IRE (black)
and 100 IRE (white), although higher values are possible. Signals above 100 IRE are
considered illegal for broadcast. North American NTSC systems set black at 7.5 IRE.
This extra 7.5 IRE is called setup or pedestal (because it pushes the entire image higher
on the waveform monitor).
How Digital Video Signals Are Measured in Final Cut Pro
The Final Cut Pro Waveform Monitor displays Y´C
B
C
R
values as percentages instead of
bit values because digital video can use 8 or 10 bits per luma sample. Using 8 bits
provides up to 256 tones from black to white, although the actual range used in Y´C
B
C
R
video is 16 (black) to 235 (white). The remaining values, 236 through 254, provide
additional headroom used to record super-white levels such as specular highlights on
shiny objects.
Percentage in Final Cut Pro
Waveform Monitor
Values for 8-bit Y´C
B
C
R
Values for 10-bit Y´C
B
C
R
–10% n/a n/a
0% (black) 16 64
100% (white) 235 940
109% (super-white) 254 1019