Two great tools in After Effects CS5 are the new Roto Brush and the inclusion of DigiEffects Freeform AE plug-in, which previously would have cost you $299 (around £195) on its own. Here's our step-by-step guide to these new tools.
The all-new Roto Brush makes rotoscoping out backgrounds a breeze – turning a job that used to take hours or days into a task that’s almost as straightforward as motion tracking. Paint in the areas you want to keep, paint in the areas you want to matte and let After Effects do the rest.
Import a clip and drag it from the Project panel onto the New Composition button to create a composition that contains your footage.
Select the Roto Brush tool and paint over the areas you wish to retain in your footage – the actor, vehicle, or other focal point. After Effects shows your strokes in green to indicate this will be kept.
Paint your background while holding Alt/Opt to show you want to matte these pixels out. After Effects paints in red to show the areas to be removed. As you paint, After Effects creates a Photoshop-style quick selection around the central object.