Masking in After Effects

One of the effects I used on some of my videos (Such as the flag on the first video and my intro movie). I used the one on the flag to make the flag take over the screen, and the one on the intro movie to give it an older, flashback look.

I started by making a circle with the mask tool, and then inverting the selection so the circle was the part that wasn't masked.

These are the settings I used form y mask. I used the feather to blur the edges of the mask.

This is how the video looks with the mask.