NewTek TriCaster 2 Elite (3 RU) - Manual (Page 161)

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for Tolerance – perhaps just 5-10, or so. Put the video source on Preview or Program Output before you do
so, to provide a larger view to help you assess your settings.
Pick your primary Color , but – before releasing the mouse button – slide the eyedropper around to different
parts the background. Watch the monitor as you do so to see how the area of transparency is affected by
different Color choices. Release the mouse when you find the color that produces maximum results.
It’s often preferable to pick an ‘average’ color from a location fairly close to the boundary between the
background and foreground regions. Now you can start to ramp up Tolerance . Bring it up slowly until most
of the background color has been eliminated, cutting away most of the background to within a few pixels of
the foreground/background boundary. Now raise
Smoothness to fine tune that edge region, and you’re
nearly done.
Before considering your settings final, make sure to test the result using a moving source. This will
sometimes reveal that overly aggressive settings cause small ‘blocks’ of pixels in the edge region to appear
to snap on and off during motion - as they either qualify or disqualify for inclusion in the resulting matte. (A
little reduction in
Tolerance and increase in Smoothness will usually resolve this problem.)
Hint: It can be useful to zoom in using Position controls when fine tuning LiveMatte.
SECTION 13.6
LIGHTING FOR LIVEMATTE
We’d like to offer a few suggestions here to guide you in preparing your set. The single most important aspect
of ‘pulling a clean key’ is lighting. The lighting should be even and diffu se. Bright ‘h otspots ’ and shadows
create different shades on the wall, and overexposed areas lack sufficient color for clean keying. (It is not
how
much light you have on the key wall, but how evenly lit that wall is.) Naturally, you want to keep your
green (or blue) screen clean and free of wrinkles, ripples, folds, tears, or other blemishes, as well.
The distance from your talent to the wall behind them can make a big difference. When the subject stands
too close to the key colored background, the key color reflects back onto the subject, creating a green or blue
fringe that is difficult to remove. If you have available space, move your subject farther away from the wall.
When good distance is out of the question, you can improve things somewhat by placing lights above and
behind the talent, lighting them from behind with a complimentary color filter over the light to ‘cancel out’
unwanted reflection (for green use a magenta filter; for blue, orange or amber. Don’t overdo back (or to p)
lighting, however. The limited dynamic range of the camera means there will be little useful color data in
badly over-exposed highlights. This can make it next to impossible to separate fringe zones (such as hair
detail) from the background (especially when this is also overexposed).