First, you need to shoot a “stack” of photos with a fixed focal length. Starting from a distance, you move closer to your subject with each new shot. […]
The framework allows you to split up a scene based on depth, and assign a different focal length perspective to each of those depths. You can make the foreground look like it was shot with a telephoto lens and the background look like you used a wide-angle one.
Watch it in action (and skip ahead ~2 minutes to get to the wow stuff):