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Chapter 12 Commotion Clip FX
Moving the Input sliders toward the middle increases the contrast in the image, and moving the Output
sliders in decreases the contrast of the image. Using the Levels effect is different from changing the con-
trast with the Brightness and Contrast effect because the Levels effect can weight changes toward the high-
lights or the shadows. You can also adjust the gamma curve with the Levels effect.
Using the Color Key effect
The easiest way to use this effect is as follows:
1 Click the eyedropper and select the color from which to create the matte.
2 Set the View mode to Matte and adjust the Min and Max values.
3 Keep adjusting until the pure blue areas of the background are solid black and the foreground
elements are solid white. The closer the Min and Max values are to each other, the harder the
matte, so try to keep the values apart to get a smooth transition.
4 Set the View mode back to Comp and make final adjustments to get a perfect matte.
GreenScreen Key
GreenScreen Key compares the green channel to the red and blue channels and creates a matte based on
the differences.
It is functionally identical to BlueScreen Key, except it is designed for footage shot against green. For
information on the use of this effect, see “BlueScreen Key” on page 677.
LumiKey
LumiKey creates a matte based on the luminance values of an image. While the other keyers base their
mattes on a particular color channel, LumiKey uses luminance, which is a color space variable.
 Min and Max -
select the minimum and maximum threshold values. Values below the minimum are black; val-
ues above the maximum are white; and everything in between is a gradation of grays between the
two values.
While it is possible to set a minimum value higher than the maximum value, Avid Liquid will always treat
the lower value as the Min value and the higher as the Max value. For example, values of Min 40 and Max
60 will be treated the same as Min 60 and Max 40.
 Invert Matte -
reverses the black and white areas of the matte.