Effect from Beth's Contest Entry

[Wheat King]

I watched some of the entries again before the voting closed and at 4 minutes in to your 40th birthday video, there is flash effect that looks like it flashes behind the funny glasses. How'd you do that?

[Maxine370]

If I can remember correctly I used track matte in this way...

I put the same picture on three tracks.
Top layer was my matte (I'm using v2 so it may be different in v3). I used extract and fiddled with it to get a nice black white balance.
Middle track was the unaltered picture with track matte applied.

Lower track was the picture again but with brightness contrast keyframed so that the flash appears behind son of the elements in the picture rather than on top of it. It only works great some of the time but when it does it is a fun effect.