Apple Motion 3 - Manual (Page 291)

Chapter 3 Basic Compositing 291
The effect that each blend mode has on overlapping objects depends on the range of
color values within each object. The red, green, and blue channels within each
overlapping pixel are mathematically combined to yield the final image.
These value ranges can be described as blacks, midrange values, or whites. These
regions are loosely illustrated by the chart below.
For example, the Multiply blend mode renders color values that fall into the white areas
of an image transparent, while the black areas of the image are left alone. All midrange
color values become translucent, with colors falling into the lighter end of the scale
becoming more transparent than the colors that fall into the darker end of the scale.
Group Blend Modes
Blend modes work differently depending on whether they’re used with groups or
layers. In particular, the Pass Through blend mode is only available for groups.
Pass Through
When a group is set to Pass Through, each object is individually blended with all
objects and groups that appear underneath it in the Layers tab. In this example, the
Swirls object is set to Stencil Luma, and the Fishes object is set to Add.
Blacks Whites Midrange color values