Adobe AFTER EFFECTS 5.5 Help Manual page 90

Adobe After Effects Help
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For more information, see "Using cameras" on page 235 and "Using lights" on page 239.
About motion blur
When you view one frame of motion-picture film or video containing a moving object, the
image is often blurred. This is because a frame represents a sample of time (in film, a
sample is 1/24 of a second long). In that time, a moving object occupies more than one
position as it travels across the frame, so it cannot be shown as a sharp, still object. The
faster the object moves, the more it blurs. The camera shutter angle also affects the
appearance of the blur.
In contrast, in a single frame of a computer-generated animation, you may not be able to
tell which objects are moving because all moving objects may appear as sharp and clear
as nonmoving objects. Without motion blur, layer animation produces a strobe-like effect
of distinct steps instead of an appearance of continuous change. Adding motion blur to
layers you animate in After Effects makes layer motion appear smoother and more natural.
You can use motion blur when you animate a layer—for example, moving a layer of text
across the screen. You cannot add motion blur to motion that already exists within a layer,
such as live-action video. If you want to smooth live-action video where you assigned a
frame rate much lower or higher than the original, use frame blending. See "Enhancing
time-altered motion by blending frames" on page 89 and "Using frame blending" on
page 89.
Note: Previous versions of After Effects included an effect called Motion Blur. That effect is
now named Directional Blur, to avoid confusion with motion blurring applied to layers.
Applying motion blur to layers
The Motion Blur switch creates a true motion blur based on the layer's movement in a
composition and what you specify for the shutter angle and phase (see "Adjusting the
shutter angle for motion blur" on page 91).
Note: For information about the Directional Blur effect (called "the Motion Blur effect" in
earlier versions of After Effects), see "Blur and sharpen effects" on page 186.
Motion Blur slows previewing and rendering, but you can apply motion blur without
displaying it in the Composition window. Use the Enable Motion Blur button ( ) near the
top of the Timeline window to control whether layers that use motion blur affect redraw
and rendering. You can also enable motion blur for all compositions when you render a
movie. For more information, see "Changing render settings" on page 281.
To apply motion blur to a layer:
Select the layer or composition you want to blur in the Timeline window, and choose Layer
> Switches > Motion Blur.
You can also apply motion blur by clicking the Motion Blur switch to place a checkmark for
that layer.
Note: A checkmark by the Motion Blur command indicates that motion blurring is turned
on for the selected layer or composition. The checkmark also appears in the Motion Blur
switch ( ) for that layer in the Timeline window.
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