What do you do when you only want an effect on one part of your image while animating in After Effects. Make an effect mask, of course, it's easy and fast.
After Effects Tips: How do I apply an effect only to a masked area in Adobe After Effects?
Make a mask on your layer. Add an effect. Twirl down the effect to reveal the Compositing Options in the timeline (does not reveal in the Effect Control panel). Hit the plus button to make a Mask Reference. Select your mask. The effect will only be applied to the masked area. You can change the modes on the mask and the feather it and have the effect opacity.
Hope you found this useful, we'll be doing some more of these quick and easy After Effects Tips in the future. Looking for some design finishing tips? Check here: http://attackmotiondesign.com/motion-design-boards-finishing-tips