User Guide

Using Help | Contents | Index Back 187

Adobe After Effects Help Applying Effects

Using Help | Contents | Index Back 187

Channel Blur

This effect blurs a layer’s red, green, blue, or alpha channels individually. You can specify

that the blur is horizontal, vertical, or both. At Best quality, the blur is smooth. Use this

effect for glow effects or if you want a blur that does not become transparent near the

edges of the layer. The Edge Behavior option describes how to treat the edges of a blurred

image. If you deselect it, pixels outside of the image are transparent, which makes the

edges of the blurred image semitransparent. Select the Repeat Edge Pixels option to

repeat the pixels around the edges, preventing the edges from darkening and becoming

more transparent.

Compound Blur

This effect blurs pixels in the selected layer based on the luminance values of a blur layer,

also known as a blurring map. The blur layer, which can be any layer that contains pixels of

different luminance values, is essentially overlaid on top of the selected layer and the

pixels of both layers are matched, one to one. Where the blur layer is black, no blurring

occurs in the same location in the selected layer. The blur layer is used only as a map; it is

not visible in the composition.

The Blur Layer speciﬁes the layer in the composition to use as the blurring map. Bright

values in the blur layer correspond to more blurring of the affected layer, while dark values

correspond to less blurring. Maximum Blur speciﬁes the maximum amount, in pixels, that

any part of the affected layer can be blurred. The Stretch Map to Fit option stretches the

blur layer to the dimensions of the layer to which it is applied; otherwise, it is centered.

Invert Blur inverts the values, so areas that were previously more blurred will be less

blurred, and vice versa.

This effect is useful for simulating smudges and ﬁngerprints, or changes in visibility due to

atmospheric conditions such as smoke or heat, especially with animated blurring layers.

Compound Blur is especially effective in combination with other effects, such as

Displacement Map (see “Displacement Map (PB only)” on page 193).

Directional Blur

This effect gives a layer the illusion of motion. At Draft quality, the effect is a blur of the

image in which each pixel is the unweighted average of its adjacent pixels. At Best quality,

the effect uses Gaussian weighting, producing a smoother, more graduated blur. The

Direction option speciﬁes the direction of the blur. The blur is applied equally around a

pixel’s center; therefore, a setting of 180 degrees and a setting of 0 degrees look the same.

A. Original B. Directional Blur C. Radial Blur