Apple Motion 5.1.1 - Manual (Page 231)

Chapter 7 Basic compositing 231
For overlapping layers with different blend modes, the bottommost pair of layers is combined
first, and that combination then interacts with the next layer up, and so on until all overlapping
layers are combined for the final image. In this case, each layer with a specified blend mode
only interacts with the image below it, whether that image is a single layer or a pair of layers
blended together.
Each of Motion’s blend modes works in conjunction with the Opacity parameter to alter the
interaction between the foreground and background layers. Adjusting a layer’s opacity lessens
the blending effect assigned to it, even as it reduces that layer’s visibility, allowing you to
customize any blend mode to better suit your needs.
Blend modes only affect overlapping layers, and have no interaction with your project’s
background color (unless the background is set to Environment). If you specify a blend mode for
a layer that doesn’t overlap anything, that layer remains as it was before.
Change a selected layer’s blend mode
Do one of the following:
m Choose an item from the Blend Mode pop-up menu in the HUD.
m Choose an item from the Blend Mode pop-up menu in the Properties Inspector.
m Choose Object > Blend Mode, then choose an item from the submenu.
m Display the Blend Mode column in the Layers list (choose View > Layers Columns > Blend Mode),
then choose an item from a layer’s Blend Mode pop-up menu.
m Control-click a layer in the Canvas, then choose an item from the Blend Mode submenu in the
shortcut menu.
m Control-click a layer in the Layers list or Timeline, then choose an item from the Blend Mode
submenu in the shortcut menu.
How blend modes work
Each blend mode presents a different method for combining two or more images together.
Blend modes work in addition to a layer’s alpha channel and opacity parameter.
To understand the descriptions of each blend mode in this chapter, it’s important to understand
that blend modes mix colors from overlapping images based on the brightness values in each
color channel in an image. Every image consists of red, green, blue, and alpha channels. Each
channel contains a range of brightness values that define the intensity of each pixel in the image
that uses some of the channel’s color.
The effect that each blend mode has on overlapping layers depends on the range of color values
in each layer. The red, green, and blue channels in 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.
Blacks Midrange color values Whites
For example, the Multiply blend mode renders white color values in an image transparent,
while black values are left alone. All midrange color values become translucent, with colors in
the lighter end of the scale becoming more transparent than the colors in the darker end of
the scale.
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