Apple Final Cut Pro 7 - Manual (Page 1323)

Motion parameters, transitions, and compositing modes can alter the results of the
Broadcast Safe filter applied to individual clips. In these cases, it’s best to create a nested
sequence and then apply the Broadcast Safe filter to the nested sequence. For more
information about nested sequences, see
“Methods for Editing Clips from One Sequence
to Another.” This is also more efficient than applying the Broadcast Safe filter to every
clip in your sequence.
Using the RGB Limit Filter
The RGB Limit filter has controls to prevent illegal RGB levels while working in Y
′
C
B
C
R
color
space.
About Illegal RGB Levels
Most video formats are recorded, edited, and transmitted in Y
′
C
B
C
R
(component) color
space. Although you may never intentionally convert your footage to RGB color space, it
is fairly certain that it will become RGB at some point—most likely during display on a
television or monitor. Video is almost always converted to RGB color space within display
devices.
When you work in Y
′
C
B
C
R
color space, levels are either described in their native color
space or they are referred to as RGB-equivalent values, meaning the values of your Y
′
C
B
C
R
video signal when it is eventually converted to RGB.
Illegal RGB levels are generally caused when certain combinations of luma and chroma
levels (in Y
′
C
B
C
R
color space) are converted to RGB color space. Even if both luma and
chroma levels are legal in Y
′
C
B
C
R
color space, the combination of these two may cause
illegal RGB levels.
Tip: The RGB Parade scope in the Video Scopes tab is useful for viewing RGB levels when
working in Y
′
C
B
C
R
color space. For more information, see “Learning to Read the RGB
Parade Scope.”
Legal RGB levels are usually defined as 0 percent to 100 percent, where 0 percent is the
lowest legal value and 100 percent is the highest. When Y
′
C
B
C
R
footage is converted to
RGB, RGB levels can be illegal in two ways: if they are below 0 percent or above 100
percent.
Note: If your video originated using a codec that is already in RGB color space (such as
the Animation codec), it is unlikely that the RGB levels are illegal.
1323 Chapter 78 Measuring and Setting Video Levels