Originally posted by Medex For me these two images (75 mm uncropped and 28 mm cropped) are different enough, I could not agree with your conclusion.
Thanks for the feedback.
The depth of field
is different because (as I mentioned in my original post) the same f/3.2 aperture was used at 75mm and 28mm. Depth of field is a separate matter, though... This demonstration deals with
subject compression at different focal lengths.
Any other slight differences are due to the fact that I took these shots hand-held, rather than on a tripod, and cropped the 28mm shot manually (with a tiny amount of rotation correction to visually match the two shots as closely as possible). It's highly probable the camera was an inch or two left / right / up / down / closer / further away between shots, or that my cropping wasn't pixel-perfect in dimensions or positioning. Even so, there really isn't
much difference between them. Remember, we're talking about a BIG gap in focal lengths... 75mm versus 28mm. If there was a difference in subject compression, you'd expect it to be very significant rather than marginal - wouldn't you agree? As it stands, if not identical, the subject compression appears to be
incredibly similar in both images... similar enough that, given the hand-held nature of the shots, I'm happy to argue compression is
the same.
Still, if you or anyone else remain unconvinced, that's fair enough. Please try it for yourself and be kind enough, if you would, to share the results (fellow members, myself included, will appreciate it). Fit a zoom lens to your camera, mount it on a tripod (my one error and omission, in my haste), and repeat the test at maximum and minimum focal lengths... or, use two prime lenses of very different focal lengths (just be sure not to move the camera when you fit and remove the lenses). Oh, and make sure your raw conversion software applies profiled lens corrections. If you correctly perform the test yourself, you
will find that "subject compression" / "perspective distortion" remains the same at any focal length. You'll reach the same conclusion