Essential animation principles (such as easing-in and out, acceleration, timing etc. – go back to this page to refresh your memory) can easily be applied in Adobe After Effects by looking at keyframe interpolations (also known as “tweening”) and making adjustments.
As we know, keyframe interpolation/tweening refers to the way the software fills in the unknown data between two keyframes. After Effects provides several interpolation methods that affect how the in-between values are calculated.
Linear
By default, After Effect will place frames/dots at equals intervals between two keyframes (linear interpolation). There will be more or less frames depending on the speed of the animation. The slower the animation, the more frames.
![Screen Shot 2018-08-20 at 10.20.40 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-10-20-40-am.png)
Any Keyframe can be moved along the Timeline to change the speed of an animation independently by clicking and dragging on it.
Easy ease
One of the 12 principles of animation is “Slow in and slow out”. Ease in and ease out is the equivalent in digital animation: When using both, the animation will slowly accelerate and slowly decelerate. This means there will be more frames/dots at the beginning and end of the motion path than in the middle.
![Screen Shot 2018-08-20 at 10.51.58 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-10-51-58-am.png)
To create an “easy ease” interpolation (wherein both easing in and out are applied), right-click on the keyframe and select Keyframe Assistant > Easy Ease (or press F9). You’ll notice that the little diamond turn into an hourglass. The Keyframe Assistant also provides options forEasy Ease Outand Easy Ease In.
![Screen Shot 2018-08-20 at 10.59.40 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-10-59-40-am.png)
Bezier Curve
Easy ease transforms the interpolation temporarily, but we can also change it spatially. We can transform a motion path that’s linear (a straight line) into a bezier curve. To do so:
- Select all the Keyframes in the Timeline by clicking on the property name (i.e: Position).
- Right-click on any of the selected Keyframe and select Keyframe Interpolation…
- Change the Spatial Interpolation dropdown from Linear to Bezier. You’ll notice that a little handle has been added to each Keyframe.
- Click and drag the handle(s) to curve the path.
- Alternatively, you can turn individual Keyframes into Beziers by activating the Convert Vertex tool (click and hold the Pen tool to select) and clicking and dragging on an anchor point.
![Screen Shot 2018-08-20 at 11.12.54 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-11-12-54-am.png)
Of course, this spatial transformation could also be combined with a temporal one (i.e: also applying Easy Ease to these Keyframes)
The Pen tool can also be used to add Keyframes along a path:
- Select the Pen tool.
- Click on an existing path at the point where you’d like to add a Keyframe
- Click and drag that new anchor point to change the shape of the path.
![Screen Shot 2018-08-20 at 11.27.17 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-11-27-17-am.png)
![Screen Shot 2018-08-20 at 11.27.25 AM](https://mmp260.files.wordpress.com/2018/08/screen-shot-2018-08-20-at-11-27-25-am.png)
More temporal adjustments
If you have more than two keyframes and want to alter the speed of the entire path while keeping the same ratio of space between each frame:
- Select all the Keyframes in the Timeline by clicking on the property name (i.e: Position).
- Alternatively you could select a series of frames rather than all of them by just clicking and dragging to create a selection on the Timeline.
- Hold the Optionkey and click and drag the last Keyframe in the selection.