Effect masking overview
Using the masking tools built into most clip effects in Final Cut Pro, you can isolate and control which areas of the video image are affected by the clip effects, including color corrections.
You can apply a color mask and any number of shape masks to a clip effect, and you can have multiple masks interact in different ways within an effect.
As with most effect parameters in Final Cut Pro, you can also animate any effect mask.
For information about using traditional masking tools to create areas of transparency in an image, see Masking overview.
Note: Clip effects in the Keying and Masks categories in the Effects Browser do not have the built-in effect masking tools described in this section.