hkelsey wrote:
I have the Canon 20mm 2.8. I do a lot of architecture, machinery, manufacturing pictures with a Canon 10D. The lens is very sharp. If you want a wider angle, I just take 2 or 3 shots holding the camera as parallel as possible and rotate about 1/2 the shot each time. When you stitch these together you can get up to a 180° picture.
The best part is the picture is not like a wide angle such as 14mm lens or so. These lenses throw the center of the picture a way back. With the stitched shot you get pretty well what you see turning your head, and the center foreground is in the right place.
I used to do a lot of travel and usually only carried a Leica M3 with the 21mm Super Angulon and 90mm Tele-Elmarit. The Canon 20mm is like the 21mm Angulon. Now I am going to get a Canon 50mm 1.4.
In what way is the Canon 20 like the 21mm SA? When I shoot at the 20mm focal length, it's more like a 35mm lens on a film camera. To sweep up the scene like that Super Angulon, I need a 14.
Stitching shots will create panoramic projection (if you use the appropriate software, like Panotools). Otherwise, perspective will have angular cusps at the stitch points, which is often usable for many subjects but not, in my view, for architecture. Panoramas are nice but not for bread-and-butter architectural work.
Two shots with a shift lens can be stitched and maintain rectilinear projection, but it will cost as much as a decent 14.
For the original poster, I'd recommend getting the Tamron f/2.4 14mm rectilinear lens. You'll only use the middle of it. I don't recall how much it distorts, but you won't notice it except for one-point perspectives. The 14 will behave like a 22.
The 15mm f/2.8 Canon lens is a full-frame fisheye. Definitely NOT what you'd want for architecture, except for special effects. If it IS what you want, consider the $150 16mm Zenitar fisheye. It's all manual and made in Russia but it works great and will save you some significant coin for that occasoinal shot.
The only choice for real wide angles in Canon is the 14L, which costs a coupla grand. I'm sure it's better than the Tamron (which I'm sure is better than my Sigma), but for the money it ought to be.
A rectilinear 15 that is a bit cheaper would be nice, but I don't know of one. The 14's are the closest equivalent to the 24mm lens on a full-frame camera, at least for now.
Frankly, if shooting wide angle were a priority for me using a digital camera, I would wait for a 10D-priced body with a full-size sensor. I figure the wait will only be a couple of years. Or if waiting wasn't an option, I would (gasp!) consider a Nikon D100 with the 12-24 narrow-format zoom, though I suspect it has barrel distortion on the wide end.
Rick "who warns that the 16-35 and 17-40 zooms have barrel distortion on the wide end, too" Denney