The speed of an action, i.e., timing, gives meaning to movement, both physical and emotional meaning. The animator must spend the appropriate amount of time on the anticipation of an action, on the action, and on the reaction to the action. If too much time is spent, then the viewer may lose attention, if too little, then the viewer may not notice or understand the action.
Timing can also affect the perception of mass of an object. A heavier object takes a greater force and a longer time to accelerate and decelerate. For example, if a character picks up a heavy object, e.g., a bowlng ball, they should do it much slower than picking up a light object such as a basketball. Similarly, timing affects the perception of object size. A larger object moves more slowly than a smaller object and has greater inertia. These effects are done not by changing the poses, but by varying the spaces or time (number of frames) between poses.
Motion also can give the illusion of weight. For example, consider a ball hitting a box.
|If the ball rebounds from the box, and the box is unmoved, we have the illusion that the box is much heavier than the ball.|
|If the ball knocks the box aside, then the effect is that the box is much lighter than the ball.|
Timing can also indicate an emotional state. Consider a scenario with a head looking first over the right shoulder and then over the left shoulder. By varying the number of inbetween frames the following meanings can be implied: