Motion Pictures

Special effects have always been one of the chief attractions of motion pictures. Special effects are generally created through animation, miniatures, or matte shots. Animation is any process whereby frames are shot individually. This can range from cartoons to sequences in which objects appear to move because the camera was stopped, the object was moved a little, and then another frame was taken. Computer-based special effects in which an object or face changes into another are also rendered one frame at a time.

Illusions of reality are created by paintings, miniatures, and false backgrounds. Miniatures are small models used for everything from the cities stepped on in Godzilla films to the space ships and buildings used in science fiction films. One of the most common special effects is a false background. In many motion pictures, the scenes of characters in a moving car are shot in a studio, using another film being projected onto a screen behind the action as a background. In older films, this projector was set behind a translucent screen and projected its images onto it from behind the action. This is called rear projection. The motion picture camera and the projector were synchronized so that a frame was projected just as the camera recorded a frame.

This system did not work well with color film. It proved difficult to keep the amount of light on the subject and the background the same, and to give them the same color. So a new system, called front projection, was invented. In front projection, the false background is projected at the same angle from which the camera is shooting. A one-way mirror is placed in front of the camera. The projected image reflects off the mirror onto the action. The camera "sees" through the clear side of the mirror. Because the camera sees from the same angle as the projected image, the actors' shadows, cast onto the background, are blocked from view by their bodies.

Slow and fast motion are accomplished by changing the rate at which frames are shot. Because film is projected at 24 frames per second, anything shot at a greater rate appears slowed down when projected at 24 frames per second. Anything shot at a slower rate seems to move faster than normal when projected. These 'special effects' have applications to motion pictures and to science. They make it possible to watch a flower growing and opening in 20 seconds, or to watch an explosion that takes 10 seconds instead of one. Watching actions slowed down is often an advantage to those studying the behavior of people or animals.

The combination of computer technology with motion picture technology has given filmmakers the ability to create increasingly elaborate special effects. Animation and graphics can be created entirely by computer. These computer-generated images can then be combined with live-action footage through a process called analog image synthesis. Using a video camera, images on film are scanned into a computer. Once in the computer, the images can be easily manipulated, and then converted back into film. Films such as Steven Spielberg's Jurassic Park made extensive use of this technology to create the illusion of dinosaurs interacting with people onscreen.

A similar process called digital compositing uses the computer-scanning technique to manipulate live-action footage as well as animation. With it, a filmmaker can make it appear that an object or face changes into another. These effects are rendered one frame at a time. Computer technology has also advanced the area of puppetry, models, and miniatures. Miniature replicas are made of larger-than-life models. The two are then connected to a computer that plots their movements so that when the miniature is moved in a particular way, the full-size model moves in the same way. Innovations such as these ensure the continued development of motion picture technology.