Adobe After Effects CS3 - Manual (Page 134)

AFTER EFFECTS CS3
User Guide
129
You can choose from the following Resolution settings in the Composition Settings (Composition > Composition
Settings) dialog box or at the bottom of the Composition panel:
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 resolution you specify.
Viewing 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.
When you preview the alpha channel, the image appears as a grayscale image, with the transparency value of each
pixel mapped to a scale from black (completely transparent) to white (completely opaque).
Note: When you choose RGB Straight, which shows straight RGB values before they are matted (premultiplied) with the
alpha channel, pixels with complete transparency are undefined and therefore may contain unexpected colors.
You can view other channel values, such as saturation and hue, by applying the Channel Combiner effect and
choosing Lightness from the To menu.
To switch between showing the alpha channel and showing all RGB channels, Alt-click (Windows) or Option-click
(Mac OS) the Show Channel button.
See also
“About alpha channels and mattes” on page 252
“About straight and premultiplied channels” on page 253
“Shortcuts for using and modifying views” on page 644
“Channel Combiner effect” on page 383
Adjust exposure for previews
You can adjust the exposure (in f-stop units) for previews with the Adjust Exposure control, which is located to the
right of the Reset Exposure button
at the bottom of a Composition, Layer, or Footage panel. Each viewer can have
its own Adjust Exposure setting.
When the Adjust Exposure control is set to a value other than zero, the center of the Reset Exposure button is orange .
The Adjust Exposure control doesn’t affect final output, only how video appears during previews. To make tonal
adjustments to a layer that appear in final output, use the Exposure effect.