When blurring a project in After Effects that has a separate background layer, you can add a blur filter over the background layer to differentiate it from the foreground. If the foreground and the background are all in one layer, you need to rotoscope the clip. After Effects has a Roto Brush tool that enables you to paint part of a clip and apply that selection across a number of frames. When you complete your selection, you can add a blur filter to the background. Tips Warnings Writer Bio
