Apple Shake 4 - Manual (Page 640)

640 Chapter 23 Color Correction
High Color
The new highest value in the image. A value of 1 equals no change.
aHi
A high value control for the alpha channel.
ContrastLum
The ContrastLum node applies a contrast change on the image, with a smooth falloff on
both the low and high ends. You can also move the center of the contrast curve up and
down (for example, move it down to make your overall image brighter). Note that this
contrast is based on the luminance of the pixel, so it balances red, green, and blue, and
you therefore do not shift your hue. So, an image with strong primary colors looks
different than an image with the same values in a ContrastRGB node, which evaluates
each channel separately.
Also note that a roll-off is built into the contrast node, giving you a smooth falloff at the
ends of the curve. This is controlled by the softClip parameter.
Parameters
This node displays the following controls in the Parameters tab:
value
The contrast value. A higher value means it pushes your RGB values toward 0 and 1. A
value of 0 equals no change. A lower value is low contrast.
center
This is the center of the contrast curve. A lower value is a brighter image.
softClip
This controls the drop-off of the curve. When increased to 1, you have maximum
smoothness of the curve.
ContrastRGB
The ContrastRGB node applies a contrast curve on each channel individually, so you can
tune the channels separately. This differs from the ContrastLum node in that it only
changes the pixel value according to its own channel. For a good example of how the
functions differ, plug a ColorWheel node into both a ContrastLum and ContrastRGB
node. Notice that the ContrastLum node is weighed away from the green values. This
also means the ContrastRGB node runs the risk of shifting the hue as you adjust your
channels.