Ever wonder how some photographers manage to take photos of buildings that are NOT leaning back?
The leaning buildings come from tilting the camera up to get the top of the building in the frame. Most lenses, even wide angle ones, aren't wide enough to get the whole building in the frame while keeping the sensor of the camera parallel with the face of the building.
The solution to this is to use a
Shift Lens, a lens that permits the lens to shift relative to the sensor of the camera, to capture the top of the building without tilting the camera. It is like climbing up on a 2-story building across from the one you're photographing, and eliminated perspective distortion.
The technical detail underlying this are complex, so Google variations on "Tilt-shift lens" to find out more.
I've started using a Canon TS-E 24mm f3.5L Tilt and Shift lens on my Canon 5d Mark II DSLR to take our architectural photographs. The quality of the images from this lens are absolutely stunning and I can't wait to go take more and more and more.
If your photos are looking like this one, consider getting a tilt-shift lens for a more professional photograph.