Manual

832 Part IX Effects
Whites
In the Final Cut Express HD color correction filters, most of the controls that you use to
correct your clips affect the whites.
Whites make up the maximum range of luma in your clip. On this gradient, controls that
affect the whites affect the rightmost three-fourths of the gradient, from gray to white. The
effect that controls have over the whites of an image start to diminish at approximately
25 percent luma, shown above. This excludes the darkest parts of your image.
When you use controls that affect only one of these ranges, all changes made to the
hue, saturation, and luma levels of your picture happen exclusively in the area that falls
within that particular range of luminance. This allows you to perform very targeted
color correction only where it’s needed, such as subtly manipulating the hue of the
highlights without touching the shadows, or vice versa.
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.
Whites