Apple Final Cut Pro 6 - Manual (Page 1031)

246 Part II Effects
Key Filters
Key filters are generally used to key out background areas of video in order to isolate
foreground elements to composite against a different background. Key filters are
commonly used with the Matte Choker filter. For detailed information on applying
these filters, see Chapter 20, “
Keying, Mattes, and Masks ,” on page 421.
Filter Result
Blue and Green Screen Keys the blue or green area of a clip and uses the selected color as
a transparency mask for compositing foreground elements against
a background scene.
A View pop-up menu allows you to look at the source of the clip
(with no key applied), the matte created by the filter, the final
matted image, or a special composite of the source, matte, and
final image for reference. A Key Mode pop-up menu allows you to
choose blue, green, or a blue/green difference as the key color. The
Color Level slider lets you specify the amount of blue or green in
your clip to key out, and the Color Tolerance slider allows you to
expand the key into adjacent areas containing other shades of the
key color.
The Edge Thin slider allows you to expand or contract the matte
area to try to eliminate fringing, and the Edge Feather slider lets
you blur out the edges of the matte to create a smoother key.
(Before you use these sliders, try using a Matte Choker filter
instead.) An Invert checkbox allows you to invert the matte, making
what was masked solid and what was solid masked.
Chroma Keyer 1 Allows you to create a key using any range of color you want,
including (but not limited to) the usual blue and green. You can
also fine-tune your composite by adjusting the color value,
saturation, and luma ranges used to define your key, together or
separately. For example, if you only want to perform a luma key,
you can disable color and saturation. Even when performing a
color key, you’ll get superior results by manipulating the Color
Range and Saturation controls separately.
Color Key Keys on any color in a clip. Color controls allow you to select a color
from your clip as the specified key color. Sometimes referred to as
chroma key.
Color Smoothing - 4:1:1
Color Smoothing - 4:2:2
Improves the quality of chroma keys and reduces diagonal
“stair-stepping” that can occur 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 DVCPRO 50, DVCPRO HD,
and 8- and 10-bit uncompressed video.
To improve the quality of your chroma key, apply the appropriate
smoothing filter to the clip you want to chroma key first. As you
add additional key filters, make sure that the Color Smoothing filter
remains the first one in the video section of the Filters tab.