Any film project is essentially a series of individual photographs moving fast enough in front of a viewer's eye to give the illusion of motion. One popular animation technique which takes advantage of this illusion is known as stop motion. Animated cartoons could be considered stop motion, as well as the appearance of a giant ape in the film King Kong or a group of dancing raisins in a popular series of commercials. Instead of filming a real ape or raisin, a model is filmed frame-by-frame, with the animator making small adjustments after each frame's exposure. When all of these individual images are projected at a rate of 24 frames per second, the animated film should look almost as natural as live actors performing the same movements. Stop motion can be a very labor-intensive and time-consuming process, which is why most of these movies are relatively short in duration.
In order to film a clay model raisin singing a Motown song, for example, the animator must first determine precisely what the finished sequence should look like. The model may have to grab a microphone, sing a line from the song, perform a spinning dance move and fall to his knees. In order to recreate this sequence, the animator would film the clay model reaching one hand towards a microphone, but only 1/24th of a second at a time. If the movement should take two seconds to perform in real time, the animator would have to shoot 48 frames and adjust the model's hand and arm very slightly after each frame. If the animator wanted to create a faster, comedic effect, he or she could shoot fewer frames and make larger movements per frame. Some early stop motion comedy sequences were shot at 8-10 frames per second and projected at 18-24 frames per second.
Sometimes an animator will first film live actors performing a scene in real time, then recreate the scene using animation drawings or models. This technique is often used in feature length animated cartoons in order to present a more realistic sense of movement. Special computer software can also be used to extrapolate all of the individual frames necessary to animate a character's desired movement. A character could be positioned on one side of a room, for instance, and the program could calculate how many frames it would take to move that character to the other side. Some animators prefer to work in teams, with individual members moving a specific character or background image simultaneously between frames.
One of the most common uses of stop motion among amateur filmmakers is the coordinated movement of inanimate objects or people. A volunteer actor could be filmed jumping in the air frame-by-frame, for instance. Since the camera does not capture the moments when the actor is on the ground, the finished film would show him or her apparently floating in mid-air. Toy soldiers could also be arranged and filmed one frame at a time to create an animated battlefield. Certain video cameras with frame-by-frame capability can also be used to create stop motion films, although the frame rate per second can be closer to 30 fps, compared to 24 fps for traditional film cameras.
Creating stop motion films can be a tedious process, with productivity measured in seconds per workday, but the finished production is often fascinating to watch.