This week's image, "Paris s'éveille," is a stereographic projection. No, I didn't know what that was either, until I read the explanation provided by photographer Alexandre Duret-Lutz (Flickr handle "gadl"), an assistant professor at Epita. And, er, actually, I'm still not sure after reading his explanation -- you can plow through it yourself at www.flickr.com/photos/gadl/sets/72157594279945875/.

But basically, it seems that Alexandre takes multiple shots (16 in this case) and builds an equirectangular panorama. Then he uses the mathmap plug-in for The Gimp image editor to create the stereographic projection from the panorama. Read his how-to for tips on doing it yourself.

And here's the equirectangular panorama from which Duret-Lutz built the stereographic projection: