Manipulate alpha channels using filters, Blur filters, Blur filters overview – Apple Motion 5.1.1 User Manual
Page 757: Manipulate alpha, Channels using filters
Chapter 19
Filters
757
Manipulate alpha channels using filters
There are filters you can use to manipulate or even replace a layer’s alpha channel. For example,
the Keying filters create transparency by generating an alpha channel based on colors or
luminance values in that layer. Keying filters are usually used on layers that have no alpha
channel information; these filters add a new alpha channel to the layers to which they’re applied.
For more information on the use of the keying filters, see
on page 487.
The process of improving a keying effect or of customizing an alpha channel created using shape
or image masks may require the use of special filters. Although you can apply any filter to a
shape or image mask to modify that mask’s effect, the filters described in this section modify a
layer’s entire alpha channel, including the sum of all masks and other filters applied to that layer.
For example, if you’ve applied a keying filter, you can use the following filters to modify the
resulting alpha channel even though no mask appears for that layer in the Layers list or Timeline.
•
Channel Blur: This filter, found in the Blur category of the Filters library, lets you selectively blur
the alpha channel. You can set the amount of horizontal and vertical blur independently.
Original (color channel)
Original (alpha channel)
Channel Blur (color channel)
Channel Blur (alpha channel)
•
Matte Magic: This filter, found in the Keying subcategory of the Filters library, lets you
manipulate various qualities of an alpha channel, shrinking, feathering, and eroding the alpha
channel to fine-tune it. For more information, see
on page 508.
Blur filters
Blur filters overview
Blur filters can be used to simulate the real-world blurring that occurs due to the depth of field in
photographed material. They can also be used to create designed effects.
For a description of each Blur filter, see the filters list in the Help table of contents (the sidebar to
the left of this window).
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