Apple Final Cut Pro 5 - Manual (Page 1208)

Chapter 20 Color Correcting Clips 421
II
Illegal Broadcast Levels
Broadcast facilities have limits on the maximum values of luma and chroma that are
allowable for broadcast. If a video exceeds these limits, distortion can appear in the
form of colors bleeding into one another, the whites and blacks of your program
washing out, or the picture signal bleeding into the audio and causing audible
distortion. In all these cases, exceeding standard signal levels can result in
unacceptable transmission quality.
For this reason, as you are performing color correction on clips in your edited
sequence, you need to make sure that the luma and chroma levels of your video stay
within the parameters referred to as broadcast legal, or acceptable for broadcast. It is
easy to inadvertently push the levels of clips in your sequence too high, so it’s
important to use Final Cut Pro scopes and range-checking options to make sure that
the luma and chroma levels you set stay legal.
Note: If your program has been accepted for broadcast, you can usually get a set of
guidelines specifying the broadcaster’s criteria for a legal video signal. The Corporation
for Public Broadcasting has a frequently cited set of guidelines for defining what levels
of luma and chroma are acceptable for broadcast. You will probably be in the clear with
most broadcasters if your program adheres to these guidelines, since they are fairly
conservative. Other broadcast companies publish their own guidelines.
The Importance of Using a Properly Calibrated Broadcast Monitor
When using Final Cut Pro color correction filters to adjust the color, blacks, and whites
of clips in your sequence, it is essential to always use a properly calibrated broadcast
video monitor to view your adjustments as you’re making them. Only an NTSC or PAL
broadcast monitor allows you to see the color and brightness of your video as it truly
looks. The image on your computer display, in comparison, does not show the color,
blacks, or whites of your video clips as they will appear during broadcast. For this
reason, the color of video on your computer display should never be used as a
reference when performing color correction.
The video monitor you use should be a professional broadcast monitor, rather than a
consumer television set. Television sets have special filters that are meant to make
video coming in off the airwaves look more attractive. These filters can cause your
video to look more vivid than it really is, fooling you into making incorrect color
correction adjustments.
Important: Make sure to always calibrate your broadcast video monitor to color bars
as described in Volume I, Chapter 23, “Using Color Bars for Video Calibration.”
Otherwise, you may be incorrectly modifying the color, blacks, and whites of your
clips to compensate for an incorrectly adjusted monitor.