So what is an After Effects Expression?
Expressions are snippets of code that, when applied to a property, manipulate the values
in ways that manual techniques cannot easily produce.
According to Adobe, an expression is "a little piece of software - much like a script - that
evaluates to a single value for a single layer property at a specific point in time."
The primary benefit of using expressions is to automate, simplify, and enhance complex
tasks that would normally require many keyframes and lots of patience.
When keyframing something like a squash and stretch, you have lots of keyframes placed
very close together with only slight changes in value.
Swapping keyframes for expressions generates data with clean and accurate results,
allowing for easy editing.
With expressions, you can dynamically link properties and effects from layer to layer,
comp to comp.
Translating a 3D position to work with a 2D effect is now possible with two lines of code
and very little effort.
A very small expression can become a huge time saver if used correctly and efficiently.
When it comes to automating trivial tasks, creating random values, or calculating the
exact length between two positions, After Effects has a solution - use expressions!
There are many cases where an expression will complicate a simple idea and can add to the
production and render times if not planned correctly.
Sometimes, keyframes are preferable to an expression for simplicity and speed.
If it's easy to keyframe, just keyframe it.
We've arrived at the end of Lesson 101: An Introduction to Expressions in After Effects
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