Wow! Very interesting.
I have been enjoying messing around with a 24mm Samyang tilt-shif I have. I wish someone would make one in that price range at the 50mm focal length. Maybe someday these guys will get in that market.
-Brian
Voila !
(Apologies to the purists for corrupting a 15mm thread )
Fotodiox TS adapter for Pentax 67 to EF - about $190. The Pentax 67 55mm f/4 lens was one of the sharpest they made for that format, really good in the FF middle of the image circle. I've had this one since my MF film days, but I see you can get them out of Japan for about $200. So you could assess the effects of 50mm tilt for about $390, and do away with the image degrading effects of very small apertures on 50 mp. (That doesn't exist

).
A couple of caveats; the tilt on the Fotodiox is a little clunky compared with a TS-E lens. (OK, it's very clunky). Also the edges of the image circle really can't do justice to the modern FF digital, so if using it for shift, rise, fall etc the results are way inferior to the Canon one. But for this money you can find out if you really like what is does before splashing out on the very expensive, but superb Canon one.
Oh yes, one other thing. It's important to get the mark III version of the lens, the one from 1989 onwards and looks like the picture above, as it is much better than the first two versions.