In this tutorial, I'll take a quick look at some ways you can enhance the timing and speed of you movements in After Effects with a few tricks and the Graph Editor. Knowing how to utilize the graph editor will really pay off when animating.
Keyframed values in the timeline default to linear interpolation. This means the values they are assigned to -- rotation, scale, effect parameters and such -- change by a constant amount from frame to frame in-between keyframes. A side effect of this is an abrupt speed change as you cross a keyframe, which is often perceived as an unpolished animation. To fix this, you can use Easy Ease.
1. Select the layer's first keyframe and apply Animation>Keyframe Assistant>Easy Ease. The smoothly begins the movement.
2. Select the last keyframe and press F0, which is the Easy Ease shortcut. This now brings the movement to a smooth stop.
3. Right-click on the middle keyframe, which will open a contextual menu that provides a third way to apply eases.
Select Keyframe Assistant>Easy Ease In and. This will cause the movement to slow down as it approaches this keyframe, then snap away with it's normal linear interpolation. Easy Ease Out has the opposite effect. Learning to apply Easy Ease and its variations will vavstly improve the look of many animations, but it's not always the cure!
A trickier challenge is smoothing out changes in values that are supposed to keep moving rather than start and stop. An example would be an animation with multiple Position keyframes such as something zigzagging across the comp from top to bottom. I've smoothed the paths out some, but there's an abrupt change in speed when it gets to the third keyframe. You an tell because of how the dots are spaced on the path (The closer the dots are together, the slower the movement is going to be. Since the dots at the beginning are spaced farther apart, it starts off quickly and gets slower towards to the end.) To make the change in speed at that third keyframe less abrupt, you make it an Auto Bezier keyframe. Right-click on the keyframe in the timeline, and it should change to an Auto Bezier keyframe, which is indicated by turning into a circle.
This smoothes out speed changes and makes it a little more believable.
The Graph Editor
Click on the Graph Editor switch along the top of th eTimleine panel. A graph will replace the layer bars and keyframes on the right side of this panel. Along its bottom are a series of switches that control how the graphs are displayed. These settings are remembered per comp, but check the image below for descriptions of each icon and what it does. Also, a shortcut key for toggling between the graph editor and timeline is Shift+F3;)