Apple Color 1.0 - Manual (Page 250)

250 Chapter 11 Color FX
The order in which the inputs are connected does not matter. Add has two parameters.
 Source 1 Bias: Controls how much of the Source 1 image is added to create the final
result by multiplying the value in each channel by the specified value. Defaults to 0.5.
 Source 2 Bias: Controls how much of the Source 2 image is added to create the final
result by multiplying the value in each channel by the specified value. Defaults to 0.5.
Alpha Blend
This node blends (similar to the Blend node) the Source 2 input to the Source 1 input in
all the areas where the Source 3 Alpha input image is white. Where the Alpha input
image is black, only the Source 1 input is shown. The order in which the inputs are
connected affects the output.
Blend
This node mixes two inputs together based on the Blend parameter. The order in which
the inputs are connected does not matter. Blend has one parameter:
 Blend: When set to 0, only Input 1 is output. When set to .5, Input 1 and Input 2 are
blended together equally and output. When set to 1, only Input 2 is output.
Darken
Emphasizes the darkest parts of each input. Overlapping pixels from each image are
compared, and the darkest pixel is preserved. Areas of white from either input result in
no effect. The order in which the inputs are connected does not matter.
Difference
The pixels from the image that’s connected to Source 1 are subtracted from the pixels
from the image that’s connected to Source 2. Black pixels have a value of 0, so any
color minus black results in no change to the image from Source 1. Since this is
subtraction, the order in which the inputs are connected matters.
Interlace
The images connected to each input are interlaced. The left input is for the Even field,
the right input is for the Odd field. This node is used at the end of node trees that
begin with Deinterlace nodes to process effects for projects using interlaced media.
Lighten
Lighten emphasizes the lightest parts of each input. Overlapping pixels from each
image are compared, and the lightest pixel is preserved. The order in which the inputs
are connected does not matter.
Multiply
The pixels from each input image are multiplied together. White pixels have a value of
1, so white multiplied with any other color results in no change to the other image.
However, when black (0) is multiplied with any other color, the result is black.