Apple Final Cut Pro 5 - Manual (Page 323)

322 Part IV Logging, Capturing, and Importing
NTSC and PAL each have specific color bar standards, and even within NTSC and PAL
there are several standards. When you evaluate color bars on a video scope, it is
important to know which color bars standard you are measuring, or you may make
improper adjustments. “SMPTE bars” is a commonly used standard.
Calibrating Brightness and Color on Analog Equipment
Broadcast video professionals use color bars to ensure that analog video shot in the field
is adjusted for accurate brightness and color and that there’s no distortion when this
video is captured by Final Cut Pro. Color bars are also used to calibrate analog output
back to tape, so that dubs of your final master tapes all have correct color and brightness.
Note: You calibrate using bars only if you use analog source tapes, such as Betacam SP
or Hi-8, and you’re capturing your material using an analog-to-digital video interface. If
you’re capturing digital video, you don’t have to calibrate the interface because the
digital data is copied exactly.
Typically, 30 to 60 seconds of color bars are recorded at the beginning of each new
videotape shot in the field. Color bars from a professional camcorder are used to
calibrate the on-location video monitor used to watch what’s being shot, so that
adjustments for brightness or color temperature made to the camcorder are made
accurately. Later, the color bars recorded at the head of each source tape are used to
calibrate the clip settings in Final Cut Pro. If you don’t have bars on your tape, see
“
Adjusting Color on Source Tapes Without Color Bars ” on page 328.
Each source tape should be individually calibrated because tapes from various
camcorders may have slightly different settings, or because the same camcorder may
have fluctuated slightly over the course of the production.
When Should You Use Color Bars?
Analog devices always need to be calibrated and adjusted, even if only by minute
degrees. This is because heat, age, noise, cable length, and many other factors subtly
affect the voltage of an analog electronic video signal, which affects the brightness
and color of the video image. Any time you are using analog video equipment, you
can use color bars and a calibrated video scope to measure and adjust the output of
a device.
Professional analog VTRs allow you to make adjustments to the output analog signal,
and many analog-to-digital video interfaces allow you to make subtle level
adjustments as well, controlled by software. However, digital devices are not subject
to any of these issues, and for the most part, you capture the exact information
stored on tape without worrying about subtle signal degradation.