Traditional animation, sometimes also called cel animation or hand-drawn animation, is the oldest and historically the most popular form of animation. In a traditionally-animated cartoon, each frame is drawn by hand.
The traditional animation process
Traditionally-animated productions, just like other forms of animation, usually begin life as a "storyboard," which is a script of sorts written with images as well as words (somewhat like a comic strip). The images allow the animators to plan the flow of the plot and the composition of the imagery.
Before true animation begins, a soundtrack is recorded, so that the animation may be more precisely synchronized to the soundtrack. (Given the slow, methodical manner in which traditional animation is produced, it is almost always easier to synchronize animation to a pre-existing soundtrack than it is to synchronize a soundtrack to pre-existing animation.) A typical cartoon soundtrack will feature music, sound effects, and dialogue spoken by voice actors.
If the budget of the production allows, often an "animatic" is made after the soundtrack is created, but before full animation begins. An animatic typically consists of pictures of the storyboard synchronized with the soundtrack. This allows the animators and directors to work out any script and timing issues that may exist with the current storyboard. The storyboard and soundtrack are amended if necessary, and a new animatic may be created and reviewed until the storyboard is perfected. Then, the animation begins.
In the traditional animation process, animators will begin by drawing sequences of animation on to paper with pencil, one picture or "frame" at a time. This is usually done in a "keyframe" process. A "key animator" will draw "keyframes" ("key" in the sense of "important") in a sequence which generally designate important points in that sequence. For example, in a sequence of a character jumping across a gap, the key animator may draw the character as he is about to leap, the character flying through the air, then the character landing on the other side of the gap. Other animators will then draw the frames in between the keyframes, resulting in a smooth sequence of drawings. Drawing these frames is known as "tweening," as animators are drawing the frames that go between the keyframes.
In high-budget animated productions, often each major character will have an animator or group of animators solely dedicated to drawing that character, whereas other animators will be dedicated to drawing special effects (such as fire or explosions), machinery, or other specialized non-characters. Most animated productions will also have one or more background artists who will paint backgrounds over which the action of each animated sequence will take place.
Timing is important for the animators drawing these frames; each frame must match exactly what is going on in the soundtrack at the moment the frame will appear, or else the discrepancy between sound and visual will be distracting to the audience. For example, in high-budget productions, extensive effort is given in making sure a speaking character's mouth matches in shape the sound that character's actor is producing as he or she speaks. (Try making "ah," "ooh" and "ee" sounds out loud, and note how your mouth will subconsciously form a different shape for each sound; good animators must pay attention to such seemingly trivial things!) Many times during a sequence's production, the unfinished sequence may be synched with the soundtrack that will be playing to make sure it adequately synchronizes, making what changes may be necessary.
Once a sequence is completed, each drawing (excluding the backgrounds) is then transferred from paper to a thin, clear sheet of plastic called a "cel," so called because they were once made out of celluloid, but are now made of acetate. The outline of the drawing is inked onto the cel, then colors are painted over it. The transparent quality of the cel allows for each character or object in a frame be animated on different cels, as the cel of one character can be seen underneath the cel of another; and the opaque background will be seen beneath all of the cels.
When an entire sequence has been transferred to cels, the photography process begins. Each cel involved in a frame of a sequence is laid on top of each other, with the background at the bottom of the stack. The composite image is then photographed. The cels are removed, and the process repeats for the next frame until each frame in the sequence has been photographed. (Each cel will have "registration holes," small holes along the top or bottom edge of the cel which allow the cel to be placed on pegs before the camera, to ensure that each cel aligns with the one before it to prevent a jittery image.) Once every sequence in the production has been photographed, a traditionally-animated cartoon is born.
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.
Take, for example, 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.
In very early cartoons made before the use of the cel, such as Gertie the Dinosaur, 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, whether that character or item moved in the frame or not. This led to a "jittery" appearance; imagine seeing a sequence of drawings of a mountain, each one slightly different from the one proceeding it.
In lower-budget productions, this "shortcut" is taken to extremes. 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 end result does not look very lifelike, but is inexpensive to produce. Needless to say, it looks more natural for a mountain to be perfectly still than a person.
Animation loops are used by virtually all animators. Some movements are repetitive (walking for instance), so a loop or cycle, i.e. an animation sequence which seamlessly repeats, is used. In the case of walking, the character is animated taking two complete steps (right foot to left foot back to right foot to tie-in to the starting position). Then the sequence can be repeated or cycled continuously - or as long as necessary. A loop may also be used in a scene of a car driving, in which the car doesn't "move" on screen but the background tracks or pans behind the car to give the illusion of motion.
In general, loops should be used sparingly and carefully lest they become obvious and distracting. If the driving car goes by the same background scenery more than 2 or 3 times, the loop is revealed and draws the attention of the audience away from the main action.
On the other hand, endless repitition has its own fascination...for an example of creative and entertaining use of cycles/loops, see Ryan Larkin's film "Walking" (National Film Board of Canada - Oscar nominee 1969).
Computers and traditional animation
Though the process described above is the traditional animation process, actual cels are becoming increasingly rare as the computer moves into the animation studio. Often, animators will now draw directly into a computer using a graphics tablet or similar device. Though outline drawings are done in a similar manner as they would be on paper, the computer makes it very fast and simple to paint color into those outlines, thus saving much time and labor in the animation process. The drawings are composited in a computer program on many transparent "layers" much the same way as they are with cels, and made into a sequence of images which may then be transferred onto film or converted to a digital video format.
Though traditional animation is now commonlny done with computers, it is important to differentiate computer-assisted traditional animation with 3D computer animation, such as Toy Story and ReBoot. However, often traditional animation and 3D computer animation will be used together, as in Don Bluth's Titan A.E. and Disney's Tarzan and Treasure Planet.
Interestingly the process has now come full-circle, and many modern video games use "cel-shading" animation filters to make their full 3D animation appear as though it was drawn in a traditional cel style. (See "List of cel-shaded video games.") It may only be a matter of time before such techniques appear in an animated series or movie.
Rotoscoping is a rarely-used method of traditional animation in which animation is "traced" over actual film footage of actors and scenery. The end result still looks fake but the motion will be remarkably lifelike. Waking Life is a full-length, rotoscoped animated movie, as is American Pop by Ralph Bakshi. The music video for A-ha's song "Take On Me" also featured rotoscoped animation.
Similar to the computer animation and traditional animation hybrids described above, occasionally a production will marry both live-action and animated footage. The live-action parts of these productions are usually filmed first, the actors pretending that they are interacting with the animated characters, props, or scenery; animation will then be added into the footage later to make it appear as if it has always been there. Like rotoscoping, this method is rarely used, but when it is, it can be done to terrific effect, leading the audience to believe there truly is a world where humans and cartoons co-exist. The most notable of such productions was the movie Who Framed Roger Rabbit? by director Robert Zemeckis; other popular live-action hybrids include the music video for Paula Abdul's hit song "Opposites Attract" and Bakshi's full-length flim Cool World.
- How An Animated Cartoon is Made
- Animation Toolworks' Library - Various essays on the animation process
- Cartoon Network | Animation "How To"