As a member of Canon Professional Services (CPS) I have the opportunity to get "evaluation" use of some of their lenses and cameras. Last night I was fortunate enough to get to use two high-end wide angle architectural lenses - the 14mm F/2.8L rectilinear and the 17mm F/4L TS-E - the later being a "Tilt-Shift" lens that is designed specifically for architectural photography.
What a TS-E lens allows you to do is to keep the vertical lines of a building from "converging". For example - take the image below taken with the 14mm tilted up to frame the Madonna sculpture at the San Xavier Mission . . .
Note that the vertical lines converge toward the top of the photograph. Now - the same subject from the same position taken with the 17mm TS-E shifted to correct for the perspective distortion . . .
My student and I spent the afternoon and evening downtown playing with the new lenses and evaluating their capabilities. I have access to them for the next few days and will be testing them thoroughly - including some astronomical work with them. So far - amazing!