Fun in Photoshop

This image was shot on the marble bridge over to the Oslo Opera, just after sunset.

The camera was placed on the edge of the bridge, with a slow shutter speed set. The focusing was adjusted approximately and then switched to manual. Every time she took a step forward, I pressed the shutter. The multiple photos were imported to photoshop and placed on different layers within the same file. I then erased each layer in such a way that the next picture would become visible.

Set the opacity to 50% while you are working, so that you can see the next layer below while erasing. Reset it when done, before saving.