Apple Shake 4 - Manual (Page 707)

Chapter 24 Keying 707
• status: Displays an image with different colors, each of which indicates what portions
of the foreground image are handled in which way by Keylight. This mode is useful
for helping you to troubleshoot your key.
• Black pixels: Areas that become pure background in the composite.
• Blue pixels: Areas that become spill-corrected foreground.
• Green pixels: A blend of foreground and background pixels.
• Pure green: Mostly foreground and dark green is mostly background.
screenColour
The primary color to be pulled, which is usually blue or green.
Note: Keylight is tuned to the primary colors and is not effective on secondary colors
(cyan, magenta, yellow). If trying to pull these colors, consider switching your image
from RGB to CMY with the ColorSpace node, pull the key, and then switch back to RGB.
screenRange
Defines the range of colors that should be keyed out. The higher the number, the more
of the background screen is removed. A value of 0 gives the smoothest key that retains
the most fine detail; a value of .3 removes all the gray levels, and may result in coarser
edges around the foreground subject.
fgBias
Foreground bias is used to reduce the blue spill on foreground objects. Keylight uses
this color to calculate which shades the screen color passes through as it interacts with
the foreground elements.
For example, blonde hair in front of a bluescreen tends to go through a magenta stage.
Setting the FG Bias to the blonde color ensures the magenta cast is properly
neutralized. This value affects both opacity and spill suppression. Return it to .5, .5, .5 to
effectively deactivate this effect.
Avoid picking strong colors for the FG Bias. Muted shades work much better. Another
way of looking at this parameter is as a way of preserving a foreground color that
might otherwise be neutralized because it’s too close to the key color. For example, a
pale green object, such as a plant, in front of a greenscreen would normally become
slightly transparent, with the background showing through instead of the pale green.
By setting the FG Bias to the pale green, it is preserved in the composite.
Note: Please don’t shoot plants in front of a greenscreen.
fineControl
The parameters in the fineControl subtree are used to make detailed adjustments to
the matte that is created by the Keylight node.
• shadowBalance, midtoneBalance, and highlightBalance: Located within the
fineControl subtree, these parameters help you when the screen area is slightly off
from a completely pure primary color—for example, cyan instead of pure blue.