Adobe After Effects CS4 - Manual (Page 212)

206 USING AFTER EFFECTS CS4
Views and previews
Last updated 12/21/2009
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“ Views (keyboard shortcuts) ” on page 744
Resolution
In the context of printing and other media with fixed linear dimensions, resolution refers to linear pixel density: the
number of pixels or dots in a certain span, expressed in such terms as ppi (pixels per inch) and dpi (dots per inch).
In video, film, and computer graphics contexts, the linear measurements of the images are variable, so it doesn’t make
sense to refer to the number of pixels per inch or any other linear measure. Consider, for example, that the same
640x480 movie can be shown on the tiny screen of a mobile device, the monitor of a desktop computer, and a huge
motion billboard. The number of pixels per inch is different for each of these presentation devices, even though the
number of pixels may be the same.
In this context, the term resolution refers to a relative quantity: a ratio of the number of pixels that are rendered to the
number of pixels in a source image. For each view, there are two such ratios—one for the horizontal dimension and
one for the vertical dimension.
Each composition has its own Resolution setting, which affects the image quality of the composition when it’s rendered
for previews and final output. Rendering time and memory for each frame are roughly proportional to the number of
pixels being rendered.
When you render a composition for final output, you can use the current Resolution settings for the composition or
set a resolution value in the Render Settings dialog box that overrides the composition settings. (See “
Render settings ”
on page 697.)
You can choose from the following Resolution settings in the Composition Settings (Composition > Composition
Settings) dialog box or from the Resolution/Down Sample Factor menu at the bottom of the Composition panel:
Auto (available only for previews) Adapts the resolution of the view in the Composition panel to render only the pixels
necessary to preview the composition at the current zoom level. For example, if the view is zoomed out to 25%, then
the resolution automatically adapts to a value of 1/4—shown as (Quarter)—as if you had manually chosen Quarter. If
a panel contains multiple views, the resolution adapts to the view with the highest zoom level. This setting gives the
best image quality while also avoiding rendering pixels unnecessary for the current zoom level.
Note: The Auto setting is ignored for compositions for which the Advanced composition setting Preserve Resolution When
Nested is selected.
Full Renders each pixel in a composition. This setting gives the best image quality, but takes the longest to render.
Half Renders one-quarter of the pixels contained in the full-resolution image—half the columns and half the rows.
Third Renders one-ninth of the pixels contained in the full-resolution image.
Quarter Renders one-sixteenth of the pixels contained in the full-resolution image.
Custom Renders the image at the horizontal and vertical resolutions that you specify.
View a color channel or alpha channel
You can view red, green, blue, and alpha channels—together or separately—in a Footage, Layer, or Composition panel
by clicking the Show Channel button
at the bottom of the panel and choosing from the menu. When you view a
single color channel, the image appears as a grayscale image, with the color value of each pixel mapped to a scale from
black (0 value for the color) to white (maximum value for the color).
To see color values displayed in the channel’s own color instead of white, choose Colorize from the Show Channel
menu.