Polyvision is the name that French film critic Émile Vuillermoz gave to a specialised widescreen film format devised exclusively for the filming and projection of Gance's Napoléon.[10] It involves the simultaneous projection of three reels of silent film arrayed in a horizontal row, making for a total aspect ratio of 4:1 (3× 1.33:1).[11] Director Abel Gance was worried that the film's finale would not have the proper impact by being confined to a small screen. Gance thought of expanding the frame by using three cameras next to each other. This is probably the most famous of the film's several innovative techniques.[12] Though American filmmakers began experimenting with 70mm widescreen (such as Fox Grandeur) in 1929, widescreen did not take off until CinemaScope was introduced in 1953.
Polyvision was only used for the final reel of Napoleon, to create a climactic finale. Filming the whole story in Polyvision was impractical as Gance wished for a number of innovative shots, each requiring greater flexibility than was allowed by three interlocked cameras. When the film was greatly trimmed by the distributors early on during exhibition, the new version only retained the center strip in order to allow projection in standard single-projector cinemas. Gance was unable to eliminate the problem of the two seams dividing the three panels of film as shown on screen, so he avoided the problem by putting three completely different shots together in some of the Polyvision scenes. When Gance viewed Cinerama for the first time in 1955, he noticed that the widescreen image was still not seamless, that the problem was not entirely fixed.[13]