Dude, WTF. Apparently you do not know what you are talking about, and you must be smoking crazy stuff. Medium Format used to be the Standard over 20+ years ago. And when using Medium Format, you used a Bellows with a wide angle lens.
Again, you apparently do not know what you are talking about. 50mm is not a lens you would use for Architecture. Before you start making suggestions, I would Strongly suggest you know the answers, before giving incorrect information.
With regard to focal length, the above stated information is totally incoherent logic.
To the OP;
As a General Rule of Thumb, any type of Architecture, whether it be Interior or Exterior, is shot with a Tilt Shift/ PC Lens. Click on the Hyper Links to see the lenses I am referring to.
Canon 17 TS-E
Canon 24 TS-E
Nikon 24 PC
When shooting Architecture, you want a lens that has a wide angle, preferably a PC/ TS lens, and a solid tripod rig, if possible (some locations do not permit tripods).
Here is a link to a photographer, I have worked with & studied under. Bryan used to use Medium Format + Bellows, but now shoots with a 1DsMKIII & 17 TS-E Lens:
http://www.moberlyphotography.com/arch_ext.html
Here is an Article, from the Canon Learning Center, about Architecture & using Tilt Shift/ PC Lenses:
http://www.learn.usa.canon.com/resources/articles/2011/intro_tilt_shift_lenses_article.shtml
One Last Thing, to anyone who says Photoshop/ LR/ Aperture, can do what a PC Lens does, doesn't know what they are talking about. To a certain extent, Software can mimic a shift lens (perspective correction tool), but it does not do what a Shift Lens does. If you want to do it right, even as an Amateur, do it right the first time, and you won't be trying to fix mistakes later. Regarding say the PC tool in Photoshop, what it does is it stretches the image to make it look straight, but if you cannot afford to lose those areas that fall outside the correction tool, then what good does the software do for you. If you do it right in camera, then your done, except for whatever post process work you choose to do.
For every job there is a right & wrong tool. If you want to do Architecture, even as a Hobby, then I would strongly suggest you consider investing into a PC Lens. A wide angle zoom lens, will not give you the same perspective or view that a PC lens will. If you decided to go the PC route, you don't have to buy new. You can buy used, and save quite a few $$$. I just did a search on the FM B&S, and there are quite a number of 24mm PC lenses for sale (
http://www.fredmiranda.com/forum/search.php).