In After Effects CC 2014 (13.0), we added a Compositing Options property group in the Timeline panel for every effect, which includes a couple of very powerful compositing controls:

By default, the Compositing Options property group includes an Effect Opacity property, which can be thought of as providing the same functionality as the Blend With Original control found in a few effects in previous versions of After Effects.

You can also add any number of mask references to an effect to constrain the area within which the effect’s operations are applied. For example, you can draw and track masks around a subject’s eyes and constrain the Change To Color effect to only operate within those two masks to change the eye color, leaving colors outside the masks unaffected. Another simple and common usage is to use a blur effect or the Mosaic effect on a tracked rectangular or elliptical mask to obscure a license plate, logo, or face, as in the example below:

To add a mask reference to an effect, click the plus sign next to the Compositing Options heading and choose a mask from the Mask Reference menu.

You can only choose a mask on the same layer as the effect. You can add as many mask references as you like. Note that you can use different masks for various effects on the same layer. Feathering, mask tracking, and mask expansion properties of the mask are honored in the constraints of the effect area.

When a mask is used as an effect mask, it is not also used as a layer mask – i.e., when a mask is used to constrain the area of an effect, the mask is not also used to modify the alpha channel of the layer. A mask that is used as an effect mask has a blue fx icon to the left of its name in the Timeline panel; clicking this icon expands the effect(s) for which the mask is used as an effect mask. Similarly, when an effect is constrained by a mask, the entry for the effect in the Effect Controls panel has a blue circle icon to the left of the effect name; clicking this icon expands and selects the mask(s) in the Timeline panel.

Brian Maffitt demonstrates the new effect masks and compositing options in a video on the Adobe website.

John Dickinson’s video overview of the new features does an excellent job showing the effect mask feature.

Go ahead and try this out now in the current version. If you’re not already a Creative Cloud subscriber, you can try the free 30-day trial. For information about purchasing a Creative Cloud subscription, see this page about plans and this page with current promotional offers.

If you want to let us know what your favorite changes in After Effects have been since After Effects CC (12.0), come and tell us here, whether your favorite change is a new feature, a bug fix, or a little tweak in behavior.