Apple Final Cut Pro 5 - Manual (Page 1178)

Chapter 19 Keying, Mattes, and Masks 391
II
Overview of Compositing Using the Chroma Keyer Filter
While you can use one of several different filters for keying, you often use more than
one filter, depending on the qualities of the video clip. In general, the process of
compositing two shots together by keying consists of seven main steps, using several
different types of filters. For more details, see “
Example: Using the Chroma Keyer Filter ”
on page 398.
Step 1: For best quality, start with the Color Smoothing filter
Apply the Color Smoothing filter to the clip that you want to key the background out
of. This filter improves the quality of chroma keys and reduces the diagonal “stair-step”
look that occurs in video clips with areas of high-contrast color.
Use 4:1:1 Color Smoothing with NTSC or PAL DV-25 video sources. (The exception is
PAL mini-DV/DVCAM, which uses 4:2:0 color sampling.) Use 4:2:2 Color Smoothing for
DVCPRO50 and 8- and 10-bit uncompressed video.
As you add additional keying filters, make sure that the Color Smoothing filter remains
the first one listed in the video section of the Filters tab.
Step 2: Apply the Chroma Keyer filter
Now you can apply the Chroma Keyer filter to the clip. Choose a color or level of
brightness to key on, and then make adjustments to select the range of color or
brightness that most effectively keys out the background, without eliminating the
details of your foreground subject, such as hair, fingers, or the edges of clothing. You
can also use the Thin/Spread slider to adjust the fringing that appears around your
foreground subject, but don’t use it too aggressively.
∏
Tip: While the Chroma Keyer filter is the fastest and easiest to use, you may find that
the Blue and Green Screen filter, in conjunction with the Matte Choker filter, can
perform a closer key on certain clips that have more subtle detail around the edges of
the foreground subject. For more information on the controls of the Blue and Green
Screen filter, see “
Key Filters ” on page 208.
Step 3: Eliminate fringing with the Matte Choker filter
After keying out as much of the background as you can without touching the
foreground subject, apply the Matte Choker filter to eliminate any faintly remaining
blue or green fringing or pixels surrounding the edge of your foreground subject.
Using the Matte Choker filter to eliminate this fringing works similarly to using the
Thin/Spread slider in the Chroma Keyer. You may find that, for some clips, the Matte
Choker filter works better than using more aggressive settings in the Chroma Keyer,
giving you a better chance of preserving as much fine detail around the edges of your
foreground subject as possible. Adjust the Edge Thin slider to the right to remove faint
areas of the key color around your foreground subject and to smooth out the rough
edges of your key.