In the Output Size group, click one of the preset resolution buttons.
In the Output Size group, choose one of the pre-formatted film or video formats from the drop-down list.
In the Output Size group, choose Custom from the drop-down list, and then adjust the Width, Height, and Aspect Ratio values manually.
Tip: Smaller images render much more quickly. For example, you can use 320 x 240 to render draft images, then change to a larger size for your final work.