Steve Hodges <shodges@wantree.com.au> writes: > Gregory Fraser wrote: > > > > Pardon my interruption but I think what Dave is talking about is > > compression as opposed to perspective. The vertical and horizontal > > placement of objects does not change from one focal length to another > > however the relative size of objects does change with focal length as > > does the apparent depth of the image. Doesn't it to you? > > The relative sizes stay exactly the same. > > And a change in perspective is pretty much defined as a change in > relative position or size of objects. > > If a object A looks twice as large as object B, then changing lenses > will not alter that relationship. > > The only exception is where the physical size (or construction) of the > lens is such that changing lenses produces a change in the position of > nodes which is a significant fraction of the object distance. > > OK, there'a another factor. If you're using a fisheye lens, an object > to one side will have its size (and shape) distorted in a way that > cannot be reproduced by a (presumably longer) rectalinerar lens. But > then it's not going to appear in the same field of view either. Good points on both of those exceptions. It's always good to be precise. -- David Dyer-Bennet, dd-b@dd-b.net / http://www.dd-b.net/dd-b/ John Dyer-Bennet 1915-2002 Memorial Site http://john.dyer-bennet.net Dragaera mailing lists, see http://dragaera.info
