Apple Final Cut Pro 5 - Manual (Page 1186)

Chapter 19 Keying, Mattes, and Masks 399
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4 Click the Select Color button to pick a color in the clip to key, move the pointer to the
Canvas (it turns into an eyedropper), then click the desired key color. Choose a color
that’s fairly close to the edge of your foreground subject, so that the area near the
subject is the first area of color you key out.
The color range you select with the eyedropper becomes transparent in the clip.
5 Next, you want to expand the keyed area to include regions of the background that
weren’t immediately eliminated by the first key. Click the Select Color button, and in
the Canvas, Shift-click another region of the background you want to key out to
enlarge the region of transparency.
After selecting the first key color (not
all of the green is keyed out) Before clicking with the
eyedropper tool
Selecting another range of color
with the eyedropper tool After selecting an additional range
of color