Resolution determines the dimensions of the image in pixels, which affects the image quality of the previewed or rendered composition. Rendering time and memory for each frame are roughly proportional to the number of pixels being rendered.

You can use a low resolution setting when animating or previewing a movie, and then increase the resolution before rendering your final movie.

For previewing purposes, you can automatically zoom in and out depending on the Resolution setting by selecting the Auto-Zoom When Resolution Changes preference (Edit > Preferences > Display (Windows) or After Effects > Preferences > Display (Mac OS)). Deselect this preference to maintain the composition’s size in the Composition panel.

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.