For a while I've been intrigued over videos where you see a panning still image, where the foreground part of the image moves faster than background. You can see examples throughout this video, for example (notice the man with glasses a few seconds in, and then the two men holding wine glasses: the background moves at a different rate):
I guess you could just use two pictures for this effect, but is that how they do it? I've also seen this effect in videos where they are using old, black and white images, where they obviously don't have two versions of the image. In that case, I was wondering if they've used a program like Photoshop to cut out the foreground portions and fill in the background portions somehow. Or maybe they have cut out the foreground and enlarged it, so that you don't see the gap in the background.
Anyhow, just wondering if anyone has any insights into this.