Apple MA434Z/A User Manual - Page 708

The transparency of the foreground is measured by calculating the difference between the dominant screen color (blue by default, otherwise the value of the screenColour parameter) and a weighted average of the other two colors (red and green). With the example of a cyan screen, there is a greater difference between the blue and the red than between the blue and the green, since cyan has more green than red. Setting the balance to 0 forces Keylight to ignore the second-most dominant color in the screen, which is green in the example. When set to 1, the weakest screen color (red) is ignored. There are three controls to tune the low, medium, and highlight ranges. • shadowGain, midtoneGain, and highlightGain: Located in the fineControl subtree, these parameters let you increase the gain to make the main matte more transparent. This tends to tint the edges the opposite of the screen color-for bluescreens edges become yellow. Decrease the gain to make the main matte more opaque. Note: You can lower the highlightGain parameter (to approximately -0.25) to strengthen weak areas in the interior of a mask that are due to green or blue casts in the highlights of foreground subjects in float images. • midTonesAt: Located in the fineControl subtree, this parameter adjusts the effect of the balance and gain parameters by changing the level of the midtones they use. For example, If you are working on a dark shot, you may want to set the midtone level to a dark gray to make the controls differentiate between tones that would otherwise be considered shadows. replaceColour Spill can be replaced by the replaceColour. This occurs only in the opaque areas of the holdout matte. This is useful with blue areas in the foreground that you want to keep blue and opaque. The replaceColour is therefore blue. fgMult Allows color correction on the foreground element. This exactly mimics the Shake Brightness node. fgGamma Applies a gamma correction to the foreground element. This exactly mimics the Shake Gamma node. saturation Applies a saturation correction to the foreground element. This exactly mimics the Shake Saturation node. 708 Chapter 24 Keying