One technique is the travelling matte, used to make Superman fly. First, actors are filmed against a blue background to make a matte, that 'travels' across the screen. The matte masks off where the actors were while the real background is filmed. Background and actor shots are then merged. Now, film-makers can produce spectacular effects using computers.
Early movie stars There have been movie stars as long as there have been movies.
In the days of the silents in the 1920s, the most famous stars were comics such as Buster Keaton and Charlie Chaplin. Chaplin endeared himself to millions with his shabby tramp character with a bowler hat and walking stick. Beautiful women like Mary Pickford and Carole Lombard gave Hollywood and movies an aura of glamour which they have never lost. But many silent movie stars failed to make the transition to talkies. Lope de Vega may have written over 1800 plays - 60 times as many as Shakespeare.