THE ILLUSION OF FILM
Film is an illusion because the moving pictures seen on the screen are not moving at all. A film is actually a series of tiny still pictures, or frames. They appear to be moving because the retina of the human eye retains the impression of an object for a split second after that object has actually disappeared. This principle is known as the persistence of vision . When we look at a single frame of film, the image persists in the brain’s visual center for a fraction of a second. Then, the next frame comes along and the brain has to catch up with the new image. Thus, our eyes and brain trick us into thinking that we see a smoothly moving image rather than a series of still ones.
Another illusion of film is known collectively as special effects, the tricks and techniques that filmmakers use when makeup, costume, and stunts are still not enough to make a scene convincing. Special-effects artists apply science to filmmaking, showing us things that no plain camera could ever photograph. Even since the introduction of computer graphics in recent decades, the films of today still rely on some special effects that have existed since the early years of cinema.
One category of special effects is called optical or visual effects, tricks made with the camera. One of the pioneers of optical effects was the French filmmaker Georges Méliès, who invented a technique called stop-motion photography. With this technique, a scene is filmed, the camera is stopped, the scene is changed in some way, and then the camera rolls again. Stop-motion photography can create the illusion of an actor disappearing on screen.In one short film, an actor’s clothes keep returning to his body as he tries to get undressed. Méliès also invented a technique known as split screen. By putting a card over the camera lens, he prevented half of the frame of film from being exposed. He filmed a scene on the uncovered half of the frame and then backed up the same strip of film in his camera. For the second shot, he covered the exposed half and took another series of pictures on the half that had been covered the first time. With the technique of split screen, it is possible to achieve illusions such as having the same actor play twins.
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