I try to decide between 6 × 12 or 6 × 17.[a href=\"index.php?act=findpost&pid=180416\"][{POST_SNAPBACK}][/a]
Ah. So you are contemplating the purchase of a dedicated medium-format panorama camera with a fixed wide-angle lens (as opposed to a rotating lens or to stitching frames taken with a regular camera).
And I would like to see the difference if a scene is shot with a 35 mm or 55 mm lens on a 6 × 12 in comparison to the same scene shot with a 72XL or 105 mm lens on a 6 × 17.[a href=\"index.php?act=findpost&pid=180416\"][{POST_SNAPBACK}][/a]
Well ... the most obvious difference between 6 × 12 and 6 × 17 is the frame's aspect ratio: 2:1 in the former and 3:1 in the latter. With 55 mm lens on 6 × 12, you'll get the same horizontal field of view as with an 18 mm lens on a 35-mm camera, or a 12 mm lens a APS-C camera. If you have one of those, simply crop the 35-mm or APS-C frame vertically to a 2:1 aspect ratio, and you'll see what to expect from a 55 mm lens on a 6 × 12 camera (without the superior resolution/image quality, of course).
With a 72 mm lens on a 6 × 17, you'll get the same (with a grain of salt) horizontal field of view as with 55 mm on 6 × 12 but less vertical field of view, according to the more extreme aspect ratio.
A 35 mm lens on 6 × 12 will yield the same horizontal field of view as a 12 mm lens on 35-mm format or an 8 mm lens on APS-C format (8 mm super-wide for APS-C doesn't exist; the shortest available currently is 10 mm---shorter lenses than that are fish-eye, not super-wide-angle).
A 105 mm lens on 6 × 17 will yield the same horizontal field of view as a 22.5 mm lens on 35-mm format or a 14 mm lens on APS-C format.
So to get a picture (pun intended) of what to expect from the medium-format 6 × 12 cm and 6 × 17 cm panorama cameras, get a 35-mm or APS-C format SLR or D-SLR camera and a super-wide-angle lens, shoot a few frames, and crop them vertically to 2:1 and 3:1.
-- Olaf