Disclaimer: This post isn't an official expressions guide by Adobe. It's meant to help users understand the power of expressions in After Effects. Being an author of this post doesn't mean that I am an expressions guru or think that I know everything. All the content that I have included in this post helped me to understand expressions in a fun way. My idea is to curate content and put it here and I intend to improve the content on this page. If you want to contribute, please share your videos in the comments below. If you would like to work with me 1:1, send me a private message. Thanks!
This post is dedicated to users who want to use expressions but don't know where to start. Expressions take the functionality of After Effects to a whole new level. Expressions are mainly used by After Effects power-users and new-comers are really intimidated by using them.
What is an expression?
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. With expressions, you can create relationships between layer properties and use the keyframes of one property to dynamically animate other layers. For example, you can use the pick whip to link path properties, so a mask can take its path from a brush stroke or a shape layer object. Expressions can save a lot of time by not having you to manually key-frame every animation.
What can I create with expressions?
Here is a beautiful example from School of Motion's Joey Korenman to showcase how expressions can be used to animate the hour and minute hands of a clock in a few simple steps.
Do I have to remember all the expressions? Not at all!
You don't have to memorize every bit while writing expressions. After Effects displays a drop-down list with a set of suggestions that it pulls from the layer names of the project. Composition names, layer names, footage names, and effect names are all pulled into auto-complete and shown in the correct context. Check out the improvements to the Expression Editor from the Spring 2019 release.
How to use the pick whip in expressions
If you don't want to enter entire expressions yourself by manually typing them, you can create an expression with the pick whip or paste it from an example or other property.
This short tutorial will help you understand how to use the Pick Whip while using expressions.
Some useful After Effects expressions:
In this tutorial from Ukramedia, Sergei shows how far a simple line of text can take you in After Effects. He talks about some useful expressions like Value, Time, loopIN(), loopOUT(), wiggle() and more. You also get a project file to try these expressions.
This After Effects tutorial from School of Motion covers a few fantastic After Effects expressions that you may have never used before.
If you want to take a deeper dive:
- Show us what you created with your first Expressions project.
- Feel free to share other tutorials or reference material that helped you understand how expressions work.
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