Originally posted by GerryL That is actually what a zoom lens does.
Not sure what you mean here. Unless you are referring the couple of *inches* a zoom lens might shift while zooming, which would have a practiclly imperceptible effect, zooming definitely does *not* change perspective. Only changing your position does that. There is no way to get a 28mm lens to emulate what an 18mm lens does by stepping back.
Quote: If however you have already been stuck with one lens focal length, you have to zoom with your feet to frame (or move your head forward or backward a bit) no matter what.
True. This can *partially* mimic the effect of a shorter focal length, although really, only with subjects that are close enough to you for the change in position to seem significant. Might take *hours* to back up enough on a subject at the horizon to get the same effect, and everything else about the picture would be changed drastically too.