Techniques Animation Part 2

The cel & limited animation
The cel is an important innovation to traditional animation, as it allows some parts of each frame to be repeated from frame to frame, thus saving labor. A simple example would be a scene with two characters on screen, one of which is talking and the other standing silently. Since the latter character is not moving, it can be displayed in this scene using only one drawing, on one cel, while multiple drawings on multiple cels will be used to animate the speaking character.

For a more complex example, consider a sequence in which a girl sets a plate upon a table. The table will stay still for the entire sequence, so it can be drawn as part of the background. The plate can be drawn along with the character as the character places it on the table. However, after the plate is on the table, the plate will no longer move, although the girl will continue to move as she draws her arm away from the plate. In this example, after the girl puts the plate down, the plate can then be drawn on a separate cel from the girl. Further frames will feature new cels of the girl, but the plate does not have to be redrawn as it is not moving; the same cel of the plate can be used in each remaining frame that it is still upon the table. The cel paints were actually manufactured in shaded versions of each color to compensate for the extra layer of cel added between the image and the camera, in this example the still plate would be painted slightly brighter to compensate for being moved one layer down.
In very early cartoons made before the use of the cel, such as Gertie the Dinosaur (1914), the entire frame, including the background and all characters and items, were drawn on a single sheet of paper, then photographed.

Everything had to be redrawn for each frame containing movements. This led to a "jittery" appearance; imagine seeing a sequence of drawings of a mountain, each one slightly different from the one preceding it. The pre-cel animation was later improved by using techniques like the slash and tear system invented by Raoul Barre; the background and the animated objects were drawn on separate papers. A frame was made by removing all the blank parts of the papers where the objects were drawn before being placed on top of the backgrounds and finally photographed. The cel animation process was invented by Earl Hurd and John Bray in 1915.
In lower-budget productions, this "shortcut" is used in a greater capacity. For example, in a scene in which a man is sitting in a chair and talking, the chair and the body of the man may be the same in every frame; only his head is redrawn, or perhaps even his head stays the same while only his mouth moves. This is known as limited animation. The process was popularized in theatrical cartoons by United Productions of America and used in most television animation, especially that of Hanna-Barbera. The end result does not look very lifelike, but is inexpensive to produce, and therefore allows cartoons to be made on small television budgets.

Shooting on twos
Moving characters are often shot "on twos", that is to say, one drawing is shown for every two frames of film (which usually runs at 24 frames per second), meaning there are only 12 drawings per second. Even though the image update rate is low, the fluidity is satisfactory for most subjects. However, when a character is required to perform a quick movement, it is usually necessary to revert to animating "on ones", as "twos" are too slow to convey the motion adequately. A blend of the two techniques keeps the eye fooled without unnecessary production cost.

Animation for television is usually produced on tight budgets. In addition to the use of limited animation techniques, television animation may be shot on "threes", or even "fours", i.e. three or four frames per drawing. This translates to only eight or six drawings per second.

Animation loops
Creating animation loops or animation cycles is a labor-saving technique for animating repetitive motions, such as a character walking or a breeze blowing through the trees. In the case of walking, the character is animated taking a step with his right foot, then a step with his left foot. The loop is created so that, when the sequence repeats, the motion is seamless. However, since an animation loop essentially uses the same bit of animation over and over again, it is easily detected and can in fact become distracting to an audience. In general, they are used only sparingly by productions with moderate or high budgets.

Ryan Larkin's 1969 Academy Award nominated National Film Board of Canada short Walking makes creative use of loops. In addition, a promotional music video featuring the Soul Coughing song "Circles" poked fun at animation loops as they are often seen in The Flintstones, in which Fred and Barney, supposedly walking in a house, wonder why they keep passing the same table and vase over and over again.


Multiplane camera
The multiplane camera is a tool used to add depth to scenes in 2D animated movies, called the multiplane effect or the parallax process. The art is placed on different layers of glass plates, and as the camera moves vertically towards or away from the artwork levels, the camera's viewpoint appears to move through the various layers of artwork in 3D space. The panorama views in Pinocchio are examples of the effects a multiplane camera can achieve. Different versions of the camera have been made through time, but the most famous is the one developed by the Walt Disney studio beginning with their 1937 short The Old Mill. Another one, the "Tabletop", was developed by Fleischer Studios. The Tabletop, first used in 1934's Poor Cinderella, used miniature sets made of paper cutouts placed in front of the camera on a rotating platform, with the cels between them. By rotating the entire setup one frame at a time in accordance with the cel animation, realistic panoramas could be created. Ub Iwerks and Don Bluth also built multiplane cameras for their studios.