Math layering nodes explained – Apple Color 1.5 User Manual
Page 297
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.
Math Layering Nodes Explained
The layering nodes shown in
use simple math to combine two
differently modified versions of the image together. These mathematical operations rely
on the following numerical method of representing tonality in each of the three color
channels of an image:
• Black = 0 (so black for RGB = 0, 0, 0)
• Midtone values in each channel are fractional, from .00001 through .999999
• White = 1 (so white for RGB = 1, 1, 1)
Bear these values in mind when you read the following sections.
Add
The pixels from each input image are added together. Black pixels have a value of 0, so
black added to any other color results in no change to the image. All other values are
raised by the sum of both values. The order in which the inputs are connected doesn’t
matter.
Add operations are particularly well suited to creating aggressive glowing effects, because
they tend to raise levels very quickly depending on the input images. Bear in mind that
the best way of controlling which areas of the image are being affected when using an
Add operation is to aggressively control the contrast of one of the input images. The
darker an area is, the less effect it will have.
Note: By default, the Bias parameters of the Add node divide each input image’s values
by half before adding them together. If the results are not as vivid as you were hoping
for, change the Source 1 and Source 2 Bias parameters to 1.
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Chapter 11
The Color FX Room