User Manual

Using Windows and Qualifiers Together
Another use of windows is to act as a “garbage matte” when used together with a qualifier.
By default, when you use a window and qualifier together, a key is only output where both the
window and qualifier intersect. This makes it easy to exclude unwanted parts of a key that are
too difficult to eliminate by further refinement of the qualifier controls.
For example, the following qualification is intended to isolate the woman’s face, but some of the
similarly colored wood and sky in the background is also included.
Instead of driving yourself crazy trying to eliminate the unwanted parts of the key by modifying
the current qualification, which is doing a great job of isolating the skin tones, you could instead
use a window to isolate her face, excluding everything outside the window, and simplifying your
job considerably.
A qualified image with highlight on
If she moves, then you can simply track the window to follow. Simple tracking is
covered in Chapter 121, “Motion Tracking Windows.”
Now with additional Power Window isolation
Furthermore, you can use the window’s Invert control to do the reverse, excluding all qualified
portions of the key inside the window, and including all qualified portions of the key outside
the window.
If you need to build more complex qualifier/window combinations than this, you can add more
windows, or you can use multiple qualifiers and windows with the Key Mixer node, which is
discussed in Chapter 126, “Combining Keys and Using Mattes.”
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