CinePaint is a free open source painting and image retouching program
designed to work best with 35mm film and other high resolution high
dynamic range images. It is the most popular open source tool in
the motion picture industry -- used in 2 Fast 2 Furious, Scooby-Doo,
Harry Potter, Stuart Little and other feature films. CinePaint is
used for painting of background mattes and for frame-by-frame
retouching of movies.

WWW: http://www.cinepaint.org/
