NewTek TriCaster TC1 (2 RU) - Manual (Page 154)

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Of course, if you choose poor settings, foreground areas may inadvertently be cut away as well. Or, some
areas that should be transparent may be only partially keyed. Good keying often requires judicious balance
between ‘too much’ and ‘too little’. Let’s consider the tools provided to help you achieve a great result.
SECTION 13.2
MATTE
The term Matte refers to a black and white representation
defining the transparent (background) and opaque
(foreground) parts of an image during compositing.
Portions of the matte that are grey are treated
as semi-transparent, which is very useful in
progressively smoothing edges between
foreground source material and inserted
background imagery.
LiveMatte supplies a digital version of this traditional tool. As you would expect, controls in this group allow
you to define and adjust the matte for the corresponding video input.
13.2.1
COLOR
Initially, LiveMatte removes a specific color from the foreground image. This color is chosen using the Color
button. To choose this key color, click on the Color sample box and keep the mouse button depressed. Drag
the eyedropper tool over one of the video monitors to choose the color you wish to remove and then release
it. T he neighboring ‘color well’ is updated to show the color selected.
Hint: Enable the Lumakey switch to disregard hue and base the effect solely on luminance.
13.2.2 TOLERANCE
No physical greenscreen is perfectly comprised of one color. Wrinkles, folds and shadows along with the
seemingly inevitable uneven lighting result in difference. For this reason, LiveMatte supplies a numeric slider
labeled Tolerance j ust beneath the Color picker.
The Tolerance setting allows you to broaden the range con sidered as the key color, including more ‘near -
neighbor’ colors to be included in the matte. A low tolerance removes only color values close to the primary
or key color. As you raise the tolerance, you extend the range of values on either side of the primary color
that will be treated as transparent. This allows you to deal with those imperfections we mentioned.
On the other hand, it may be that there is (usually unplanned for) detail in the foreground that is somewhat
similar to the key color. Reducing
Tolerance may allow you to prevent unwanted holes appearing when the
subject opts to wear his St. Patrick’s Day tie.
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FIGURE 168