----- Original Message ----- From: "David Dyer-Bennet" <dd-b@xxxxxxxx> To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@xxxxxxxxxxxxxxxxxx> Sent: Thursday, August 30, 2007 11:48 Subject: Re: Angle of view..... : And such photos should make *very* clear that there's no such thing as : "telephoto compression". Perspective depends entirely and solely on the : physical location of the camera, the lens focal length does *not* change : that. Crop the relevant portion out of the 24mm shot and compare it : with the 200mm shot taken from the same location and the perspective is : the same, there is no "telephoto compression". : : (Sorry, I've seen several people use that phrase here just recently, and : it's just plain *wrong* in attributing the perspective effects to the : lens used.) me earlier: differing focal lengths (obviously) have different angles of view.. full frame images are possible using these various lenses which exhibit either compression and expansion without the need to crop. by this I mean, you could easily get almost all the images you want with your widest lens and then cropping out the center, but it really doesn't give you a lot to work with if you want the compression of a 400mm from say 50 meters from your subject and you use a 21mm lens! (you'd be cropping out the tinniest portion of the image) perspective & compression are oft misused terms to be sure.. however as much as relative positions is the cause (and that is the *only* cause of perceived 'compression' or 'expansion') the effect of compression is rarely noticed in photographs taken using shorter lenses as the portion is question is generally 'background' to the main subject. - I've done a series of shots to illustrate that cropping wide angles without changing relative position will give the same result as a long lens in the past using a range of lenses from 17mm to 1200mm for student education purposes, and similarly I did a rather lengthy excersize showing a wide angle effect can be replicated by stitching long lens shots together too! Though that was as educational for me as them, as many wide angles seemed to have more than one focal length across the lens and duplicating the *exact* result of lens "A" was often impossible with longer lenses and it was a lot more work ;) Interesting effect though. And it made it quite clear why different lenses are necessary. Along a similar path, I have done a series of panoramas using multifocal lenses with the longer focal lengths used at the edges and shorter in the middle to reduce the distance distortion effect one usually gets sticking to a single focal length.. that is to say if I had a road in front of me (or any straight, horizontal and perpendicular artefact low in the frame) the image didn't end up with that characteristic U shaped line but looked a heck of a lot more like the way I perceive it in real life :) The changing DOF through the final resulting image has a slightly surreal quality to it that's kinda pleasing :) karl
