Key frame

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In animation, key frames (also keyframes) are the drawings which are essential to define a movement. They are called "frames" because their position in time is measured in frames on a strip of film. A sequence of keyframes defines which movement the spectator will see, whereas the position of the keyframes on the film (or video) defines the timing of the movement. Because only two or three keyframes over the span of a second don't create the illusion of movement, the remaining frames are filled with more drawings, called "inbetweens".

[edit] Key frames of traditional animation

In the workflow of traditional hand-drawn animation, the senior or key artist would draw the keyframes, then, after testing and approval of the rough animation, handing over the scene to his or her assistant. The assistant does the clean-up and the necessary inbetweens, or, in really big studios, only some breakdowns which define the movement in more detail, then handing down the scene to his assistant, the inbetweener who does the rest.

[edit] Key frames of computer animation

In computer animation this workflow is basically the same. The animator creates the important frames of a sequence; then the software fills in the gap. For example, in Adobe Flash, the animator can specify, in keyframes, the starting and ending position of an object, such as a circle. Flash smoothly translates the object from the starting point to the ending point. This is called tweening. The animator can correct the result in any point in time, shifting keyframes back and forth to improve the timing and dynamics of a movement, or change an inbetween into an additional keyframe to further refine the movement.

There is also an animation technique known as keyframing. Contrary to tweening, every frame of a keyframed computer animation is directly modified or manipulated by the creator, such that no tweening has actually occurred. This method is similar to the drawing of a traditional animation, and is chosen by artists who wish to have complete control over the animation.

[edit] Key frames of video editing

In video compression, a key frame is a frame encoded without reference to any images in another frame, meaning it contains the entire image as it appears on that frame. In this context, it is also often referred to as an intra frame or I-frame. It is often followed by one or more inter frames which are calculated from the preceding key frame.

In non-linear digital video editing as well as in video compositing software, a key frame is a frame used to indicate the beginning or end of a change made to the signal. For instance, a key frame could be set to indicate the point at which audio will have faded up or down to a certain level.

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.