ADOBE AFTER EFFECTS 7.0
User Guide
354
To exactly position an effect
After Effects renders all effects using subpixel positioning, a highly accurate interpolation that calculates a layer’s
position to thousandths of a pixel. Effects are calculated to a level of precision higher than the resolution displayed
on-screen, which results in smooth, high-quality effects and animations. Positioning with subpixel accuracy may
soften pixels when used with blending or smoothing effects.
1
Choose View Options from the Composition panel menu and then select Effect Controls to make the effect points
visible.
2
Select the effect you want to position in the Effect Controls or the Timeline panel.
3
Zoom in on the layer in the Composition panel. The more you zoom in, the more accurate you can be. Effect
points for effects are interpolated throughout the area of the image.
Note:
A layer must be set to Best quality to take advantage of subpixel accuracy. However, for faster editing, you can keep
layers at Draft quality until you render a finished movie.
Using Noise & Grain effects
About grain and visual noise
Almost every digital image that was captured in some way from the real world contains grain or visual noise caused
by the recording, encoding, scanning, or reproduction processes and equipment used to create that image. Examples
include the faint static of analog video, compression artifacts from digital cameras, halftone patterns from scanned
prints, CCD noise from digital image sensors, and the characteristic speckle pattern of chemical photography, known
as
film grain
.
Noise isn’t necessarily bad; it is often added to images to create a mood or tie elements together, such as adding film
grain to a computer-generated object to integrate it into a photographed scene. However, noise can also be unwanted
for aesthetic reasons. Archival footage or high-speed photography may appear unpleasantly grainy; digital
compression artifacts or halftone patterns may mar the image, or noise may interfere with technical processes such
as bluescreen compositing.
There are also technical reasons to reduce noise. For example, compression algorithms usually achieve smaller file
sizes when the input material is less noisy, so noise reduction is a valuable preprocessing step for applications such
as DVD creation and video streaming.
See also
“Adobe Media Encoder Filters options” on page 614
About grain effects
Effects such as Add Grain, Match Grain, and Remove Grain allow you to manipulate grain that appears more or less
evenly over the whole image. Grain effects can’t correct image problems that affect only a few pixels, such as dust,
salt and pepper noise, or analog video dropouts.
The Add Grain effect generates new grain from nothing; it doesn’t take samples from existing grain. Instead, a
number of parameters and presets for different types of film can be used to synthesize different types of grain.
Summary of Contents for AFTER EFFECTS 7.0
Page 1: ...Chapter 1 User Guide...
