Apple Color 1.0 - Manual (Page 244)

244 Chapter 11 Color FX
This multiplies the color with the corrected image (remember, disconnected inputs
always link to the corrected image data). Because of the way image multiplication
works, this tints the lightest areas of the image, while progressively darker areas are less
tinted, and the black areas stay black.
In a slightly more complicated example, the image is processed using three nodes: a
Duotone node (which desaturates the image and remaps black and white to two
customizable colors), a Curve node (to darken the midtones), and a Blur node. The
result is connected to one input of an Add node (with both bias parameters set to 1).
The Duotone, Curve, and Blur nodes tint, darken, and blur the image prior to adding it
to the corrected image (coming in via input 2), and the result is a diffusion effect with
hot, glowing highlights.