Which is right for you?
The first is just a standard half way inbetween like the one shown here.
The second way to approach a big movement is with a "swish".
The swish uses multiple images of the character's body part that is moving fast, in this example, it's the head.
The leading part is drawn solidly, with the trailing part showing multiple images each one fading away more and more. When animation was done on cels, the trailing images would be painted in what is called a "dry brush" effect. Normally, the paint would be applied wet, in blobs on the back of the cel. The dry brush effect is done by wiping the brush off slightly and then painting the remaining paint in strokes on the cel so that it has more of a streaking look.
Here's a sample image from the cartoon, "Northwest Hounded Police".
This is a side-to-side head take.
The third option is to use a "smear".
The smear basically stretches the image of the moving part of the body so that it looks as though it is taking up all the space from the beginning of the move right through to the end position. It causes the image to look severely distorted, like this:
The entire area of the body part is painted in solidly. Sometimes it is shot on two's and sometimes on one's depending on how fast you want the move to appear.
Here are a bunch of sample images from some Bob Clampett, Warner Bros cartoons: "Baby Bottleneck" and "The Great Piggy Bank Robbery".
How insanely amazing are these??!
There are tons of other examples in many of the Warners cartoon. If you have the DVD sets, take a look through them single frame.
Here are some more examples from Bob Clampett's "Kitty Kornered".
