Timing refers to how events are distributed in time. In nature it's greatly varied, though always limited to some specific range, naturally. Being good with timing is a crucial ability for animators, that requires study and experience.
Why is timing so important for animation? Because it is all-pervasive:
- The very basics of frames, keyframing and interpolation curves have direct relation with it.
- The Physics of motion: objects with different masses and the external forces applied on them define specific velocities for each event based on a number of variables.
- Each creature has its own timing, down to how each part moves. This varies with specific characteristics, health condition, thoughts, emotions.
- Not only characters speak in different timings according to the above reasons, it also depends on the language they are speaking.
- Lastly, timing is involved in all aspects of a production: budget, complexity, duration of each scene and of the whole film, synchronization of images and recorded dialog, etc.
Timing is essential to animation, it gives meaning and personality to the movements.
In the very beginning, animators used Timing to differentiate slower and faster actions. As the art began to mature and a whole new level of quality was pursued, another kind of timing came into play: acting's timing, which soon became a crucial and very powerful tool for character animation. With it we can demonstrate personality, thoughts, feelings, state of health and peculiarities.
Finally, the very mood of the scene can be determined and played with by variations in edition, camera movement, music, voices and sound effects, etc. Timing is everywhere.
The more frames a (part of a) movement takes, the slower and smoother it will be on-screen. And vice-versa: the less, the quicker and crisper.
Varying the timing of successive (pieces of) actions is the key to fluid, believable and interesting animations.
Timing alone can be used to determine the weight of two colliding objects. Without considering other factors: the slower an object moves after being hit, the heavier it seems to be in relation to the one that hit it.
A heavy character will have slower movements than a lighter one, in general.
An example from The Illusion of Life
To illustrate the most basic aspect of timing in animation, let's consider a character turning his head. We have two extremes (main poses), one with the head turned to the left and the other with it turned to the right. The number of frames between these two poses will determine the timing of this trivial action. But what will this timing determine? It will influence how we “read” the sequence. Again, remember that more inbetweens mean slower movement.
- character turns head from left to right.
|Number of inbetween frames||Impression about what happened with the character|
|0||has taken a strong hit that almost snapped his head off|
|1||has been hit by considerable force, e.g. by a frying pan or a brick|
|2||has a nervous twitch, a muscular spasm|
|3||the character is dodging something thrown at him, maybe the pan|
|4||is giving a crisp order: “Go on! Move!”|
|5||is calling someone in a friendly manner: “Come on! Here!”.|
|6||is admiring a beatiful girl or his dream car and turns head to keep looking|
|7||is examining something carefully|
|8||looks for a can on the shelf|
|9||considers, thinks about something carefully|
|10||is stretching a sore muscle in his neck|
How does an animator know how long an action should take? How many frames for a step on a walk cycle or to walk or run across a given distance? How many for an eye blink, a yawn, a jump? We need this kind of information all the time...
Well, estimate! That's part of the fun of being an animator. Studying references, like movies, is one way to improve your overall sense of timing and also to solve a quick doubt. In some cases, you can perform the motion yourself and guess or time it -- we're talking about motion as complex as an eye blink, not roundhouse kicks, here!
Finally, there are multiple choices for the number of frames per second (fps):
|video (most PAL systems)||25|
An action, like a walk, a jump or whatever, animated at 24 fps will play faster when shown at 30 fps, for example. Animators who have to create for more than one medium need to keep that in mind and be able to "translate" their timings from one to the other.
Note: this is not about conversion from one format to another, like from cinema to video (check Telecine). That is a distinct can of worms and in principle not something an animator has to worry about.
"... is the variation of the accentuation of sounds or other events over time." 
Professional animators study. Live or filmed performances of actors can also be great references, as well as good animations. Watching video footage at normal speed, but also frame by frame is a great way to reach new levels of understanding about movements and timing.
”Ones or Twos”
In traditional american animation scenes are drawn at 12 frames per second, each of them doubled to be shown at 24 fps. This is known as animating “on twos” and saves a lot of work and time. But certain passages with fast character movement or with camera panning, for example, don't look good this way, they have to be animated frame by frame, “on ones”.
Animes are usually drawn at 8, instead of 12 fps, except for the parts where more is needed, like explained above. That means less fluidity in general, but with even less frames to animate, the extra time can be used to improve the drawings, add shadows, etc. In both cases, interesting trade-offs.
Summer of documentation 2006 -- Willian 07:20, 5 July 2006 (CEST)