----- Original Message ----- From: gfen Subject: Re: Pentax Upgrade Follow-Up & Q
The lenses need to be combined with the longer focal length closest to the camera, and the short focal length reversed onto the front of it. I don't know the formulae for what magnifications to expect, but I got a pretty good blow up of my computer screen with the 28mm reversed onto the 150mm. Your problem might be related to the zoom lens causing vignetting. I've never tried it with a zoom (never will, either), but with primes, the image is full frame. William Robb > On Wed, 20 Nov 2002, William Robb wrote: > > Combining lenses can increas magnification. > > Can someone give me a little detail on this, please? I just poked around a > bit the omer night by holding an FA28/2.8 in front of an FA28-70/4. Just > looking through teh finder shows me a circle in the middle of the image, > not a full frame.. That's not whats supposed to happen, is it? Shouldn't I > get a full frame image? Or, is it because I was using a lens in normal > position that had a smaller aperature than the reversed lens? > > I did one quick websearch which said that circular image was normal, but I > can't imagine that's correct.. if it is, it seems downright infuriating, > and I can't figure out how anyone deals with it.
