To fully understand the concept of animation one must understand the origins, progressions and advances it has made throughout time. In the beginning animations started out as very simple drawings drawn adjacently that represented the progression of movement. The earliest of which goes back to Paleolithic cave paintings. The artists of these paintings illustrated animals with multiple legs in superimposed positions. These paintings were obvious attempts to depict movement. Over time these attempts have progressed into what we know now as animation.
The discovery of the concept of ‘Persistence of Vision’ was a major break through which lead to the creation, development and advancement of animation as we know it. This concept was discovered in 130 A.D. by the Greek astronomer Ptolemy. The concept, basically, is founded on the idea that the human eye after seeing an image will retain that image for a brief period of about 1/10th of a second. The human eye can detect movement in frame rates a slow as 10 images per second and sometimes slower. Movements, however, at frame rates below 16 frames per second appear choppy. Frame rates above 16 frames per second will make movements more smooth and continuous. The total number of frames in a movement can determine the fluidity and realism of action within in an animation.
This concept of 'Persistence of Vision' lead early inventors of the late 1800's and early 1900's to create crude animation devices such as the Thaumatrope, the Phenakistoscope, and the Zoetrope. These devices simply flashed 2 or more images in front of the eye in a quick succession to create the illusion of movement. These crude devices were limited, however, by the number of total frames they could show.
Throughout the early 1900's artists were experimenting with the idea of animation and were actually creating short films, and some full length cartoons as well.
By the 1930's Walt Disney had assembled a team of artists in Los Angeles, California. He located the team and his studio near the other major film production houses of the day. This ideal location helped Disney's success tremendously as his team was, in effect, in competition with the mainstream film production houses of the day.
Walt Disney's team was responsible for developing the production techniques that became the foundations of animation. These techniques were called "The 12 Principles of Animation". Disney’s twelve principles were the key factors that brought the art of animation through its early development and advancement stages. They have also made animation what it currently is. Most animators today still use these techniques to bring their ideas to life in movies, television, the web and video games. I will discuss Disney’s twelve techniques in detail to illustrate the ground breaking processes that Walt's art and animation team created.
Squash and Stretch - is used very often in most animations today. It gives the illusion that characters have volume, and weight as they move. During a flying scene where a main character would travel through the air and then collide with a larger fixed object such as the ground, a wall, or building the main character may squash or ‘splat’ against the surface of the larger fixed object. This illustrates the term ‘squash’. An example of stretch would be a scene where a main character is holding another character from falling over the edge of a cliff to prevent him from falling, however, the weight of the other character is causing the main character’s body to strech out and elongate. The two principles can also be used together for added effect such as in a moon walking scene where the main character is bouncing as he takes one step after another. Using Squash and Stretch in this instance by making parts of the character’s body to squash after his foot makes impact with the ground surface, and then stretch up as he continues to bounce up again, would exaggerate the characters movement and give him more appeal.
Anticipation - is the action that happens which leads up to a larger action. These actions prepare the viewing audience for the major actions. For example before a character makes a running jump, he must first takes a few steps back and compress his body down in preparation for the action of the jump.
Staging - this principle directs the attention of the audience to the idea or the storyline of the animation. Staging is meant to clearly portray the storyline to the audience by cutting down on unnecessary and confusing portions of an animation. Examples of staging are the scenes used, camera angles used, depth of view of shots used, number of characters used in each scene, number of actions taking place in the same scene. The director or animator needs to keep a proper consideration of each of these parameters when creating a movie. Too little or too much of any of these parameters can leave the viewing audience confused and/or unaware of the storyline or main idea of the animation.
Straight Ahead Animation - animating an action from beginning to end, drawing one subsequent drawing after another without any guidelines until the action or scene is complete.
Pose to Pose Animation - animation when key frames of an action sequence are drawn first and then the frames between the key frames are drawn afterwards. This controls the consistency of the speed of an action, and also the proper proportions of characters and objects within the action sequence. In Pose to Pose animation the animator can plan out and have more control over the actions in a movie, and he doesn't necessarily have to draw each frame of the animation until later.
Follow Through - the following reactions or actions that follow the main actions of a character or object. For example in a scene showing a line of cars traveling quickly down a road, bumper to bumper, the lead car stopping would be the main action, and the following cars running into each other and hitting each car that is respectively in front of it would be the reaction. Another example of Follow Through could be a scene where a cowboy on a horse is riding quickly through the desert while kicking up lots of dust. As the rider pulls back on the reigns and the horse comes to a stop, the horses tail and main hair will still push forward until they gradually come to stop and catch up with the action of the horse. Also, the dust behind the horse that was also traveling in the wind in the same line of action behind the horse may also keep traveling past the horse once he has stopped and it may travel for some time until eventually slowing down to the speed it was at before the horse came traveling by. This is Follow Through.
Overlapping action - this is very similar to Follow Through in that it is basically the same thing except that it is usually used when a character is beginning an action or changing direction or speed. An example of Overlapping would be when a skydiver is jumping out of a plane; he pulls his chute cord and the chute travels up and away from the skydiver until it opens and/or reaches its full length. At that point the chute then finally catches up to speed with the falling skydiver. This action of the chute following him or being dragged through the air by the skydiver is Overlapping action.
Slow In and Slow Out - this is the process of making the beginnings and ends of an action more fluid and smooth by gradually decreasing and increasing respectively the number of frames per second during these periods of time. Slow Ins and Slow Outs can be used to make an action sequence more realistic. During a portion of a sequence where action is slow, the animator may want to soften the action and make it more life like. At this point he will add more frames to the sequence to show a lot more of the smaller details of the action(s). On the other hand, during a faster action sequence he may want to use less frames to exaggerate the speed and distance an object or character is moving.
Arcs - these refer to the movements of objects within a scene moving in a circular or arc like fashion. Arc motions make a character or object move more naturally. Non-arced motions can cause a character's movement to look mechanical or robotic. Most objects in nature and reality (aside from mechanical devices) move in arcs due to gravity, and links or connections to other objects. An animal’s leg for example would move in arc like motions because it is attached to the animals shoulder or hip. A play ground swing would be another good example. In the case of the playground swing gravity and the point where the chains are attached overhead would affect the travel of the swing and cause it to travel in an arc like motion..
Secondary action - The actions which support and re-enforce the main action within a sequence. An animation of a boxing match could be supplemented by the secondary actions of onlookers cheering and waving their arms around, and possibly throwing things into the air, photography flashes going off, and the referee could also be making movements and gestures that would enrich the main actions ( the fight ) of the scene.
Timing - this refers to the time an object begins an action, the amount of time an object spends following through an action, and the time an object finishes an action. It can make the intent of the action of a character more understood. Timing can also make an action look more or less realistic depending on how close a character or object's motion is timed in relation to real life natural movement. An animator has to think about how much movement he wants per frame to achieve the desired speed(s) that best illustrate the type of movements he wants to create.
Exaggeration - this refers to the exaggeration of an action which adds more intensity or feeling to a movement. Exaggeration is used to give the actions in a sequence more appeal than true to life, precise, realistic actions. An example of exaggeration would be, let's say, a weightlifting character struggling to lift a barbell loaded with weights. To illustrate his struggle, effort, strength, and the weight of the barbell the animator could exaggerate his facial expressions, the shaking of his elbows and knees, the slight bending of the barbell, and maybe the final movement of him actually lifting the barbell and the flexing of his muscles ( for comedic effect and additional character appeal ). Squash and stretch are one form of exaggeration.
Solid Drawing - this refers to the classical sense of drawing such as of real life or still life drawings of 'real' things or 'real' people. Solid Drawing is the de-lineation of flat 2 dimensional cartoon drawings. Solid Drawing (3 dimensional drawing) gives a character or object dimension, volume, and weight. Solid Drawing brings more volume and realism to characters and objects.
Appeal - this has to do with a character or scene's ability to draw and capture the audience’s interest. A well developed character's personality, wants, needs, movements, actions, and reactions are a big part of his 'appeal'. The character's appeal would be that quality about him that causes the viewing audience to feel an emotion or think about him in a certain way. A character or scene with good appeal will help establish a greater emotional connection between itself and the viewing audience.
The afore mentioned principles are most times exaggerated when used in cartoons or animation shorts while full length cinematic movies typically use them more subtly. While developing these techniques Disney's studios began humbly with such movies as their black and white "Steamboat Willie"( 1928 ), and has progressed to more realistic films such as "Snow White and the Seven Dwarfs"( 1937 ), and "Bambi" ( 1942 ). Today Disney's animation team is still employing these foundational principles in their films. As animation now moves on into the new world of computer aided drawing and three dimensional animation, technology is changing, yet, these twelve principles are techniques that will not fade away.
Resources
http://en.wikipedia.org/wiki/Persistence_of_vision
http://en.wikipedia.org/wiki/History_of_animation
http://www.privatelessons.net/2d/sample/m01_02.html
http://features.cgsociety.org/story_custom.php?story_id=1429&page=
http://www.animationtoolworks.com/library/article9.html