User Manual

Color Channels (RGBA)
The filter defaults to operating on R, G, B, and A channels. Selective channel filtering is possible
by clicking each channel button to make them active or inactive.
NOTE: This is not the same as the RGBA checkboxes found under the common
controls. The node takes these selections into account before it processes the image,
so deselecting a channel causes the node to skip that channel when processing,
speeding up the rendering of the effect. In contrast, the channel controls under the
Common Controls tab get applied after the node has processed.
Gain
The gain slider is a multiplier of the pixel value. A Gain of 1.2 makes a pixel that is R0.5 G0.5
B0.4 into R0.6 G0.6, B0.48 (i.e., 0.4 * 1.2 = 0.48) while leaving black pixels unaffected. Gain
affects higher values more than it affects lower values, so the effect is most influential in the
midrange and top range of the image.
Lift
While Gain scales the color values around black, Lift scales the color values around white. The
pixel values get multiplied by the value of this control. A Lift of 0.5 makes a pixel that is R0.0
G0.0 B0.0 into R0.5 G0.5, B0.5 while leaving white pixels unaffected. Lift affects lower values
more than it affects higher values, so the effect is most influential in the midrange and low
range of the image.
Gamma
Values higher than 1.0 raise the Gamma (mid-gray), whereas lower values decrease it. The
effect of this node is not linear, and existing black or white points are not affected at all. Pure
gray colors are affected the most.
Contrast
Contrast is the range of difference between the light to dark areas. Increasing the value of this
slider increases the contrast, pushing color from the midrange toward black and white.
Reducing the contrast causes the colors in the image to move toward midrange, reducing the
difference between the darkest and brightest pixels in the image.
Brightness
The value of the Brightness slider gets added to the value of each pixel in the image. This
control’s effect on an image is linear, so the effect is applied identically to all pixels
regardless of value.
Saturation
Use this control to increase or decrease the amount of Saturation in the image. A saturation of 0
has no color, reducing the image to grayscale.
Low and High
This range control is similar to the Gain control in some respects. If Low gets anchored at 0.0
and the High value gets reduced from 1.0, the effect is identical to increasing the gain. High
values get multiplied by the inverse of the high value. (e.g., if high is 0.75, each pixel is
multiplied by 1/0.75, or 1.3333).
Leaving the high anchored at 1.0 and increasing the low is the same as inverting the image
colors and increasing the gain and inverting it back again. This pushes more of the image
toward black without affecting the whites at all.
Chapter – 85 Color Nodes 1851