NewTek TriCaster 2 Elite (3 RU) - Manual (Page 159)

P a g e | 141
a video monitor to choose the color you wish to remove and release it. The neighboring ‘color well’ is updated
to show the color selected.
Hint: Enable the Lumakey mode to disregard hue and base the effect solely on luminance.
13.2.3 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, when you choose the classic
LiveMatte mode, a numeric slider labeled Tolerance is provided.
The Tolerance setting allows you to broaden the range considered 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.
13.2.4
SMOOTHNESS
In the classic LiveMatte mode , Smoothness defines a further tolerance factor (LiveMatte ULTRA mode handles
this automatically). We want our keyed foreground to blend smoothly into the background – rather than to
stand out in hard relief like a postage stamp or decal. Smoothness serves this purpose, by defining a falloff
zone of partial transparency. Don’t overdo it though, as aggressive settings can cause the foreground to
become unnecessarily ‘muddy’.
13.2.5 LUMA LIMIT
When working with poorly-lit backgrounds (or poor-quality footage), the color Tolerance range separating
the foreground (talent) from the background can be extremely narrow. This problem can be aggravated by
the subject
’s choice of clothing, or when there are harsh shadows. There is often a strong chroma component
(and associated chroma noise) in dark foreground areas. The ‘noise’ may be partially or completely
transparent when tolerances are critical. Because the noise varies over time, ‘holes’ in the foreground can
result, and even worse these may flicker on and off from one frame to another.
Classic LiveMatte’s Luma Limit control makes it possible to overcome this issue. In essence, it restricts the
chromakey operation based on luminance (brightness) values. Dark foreground areas which typically cause
the problems just described normally have quite different luminance values from the background color,
which is usually brightly illuminated
. In simplest terms, problem areas of this type can be decisively ‘pulled’
back into the foreground by pre-filtering the chromakey effect around a luminance threshold.
Generally, try to set up the best key you can before raising the Luma Limit from its default value of zero (no
effect). Then gradually raise the limit until you are pleased with the result.