On Tue, 04 Oct 2005 19:41:31 +0200, keith_w <[EMAIL PROTECTED]> wrote:
Godfrey DiGiorgi wrote:
On Oct 4, 2005, at 9:55 AM, Mark Roberts wrote:
M42 and K-bayonet have the same register...
Lens mount body flange-to-film plane measurement?
Yes.
...and very similar to Nikon
bayonet. That's why there are no adapters I know of that will allow
infinity focus.
There used to be a K-to-M42 adapter that did allow infinity focus. It
contained one or more optical elements to make this work. ...
Mark, or somebody, didn't leave his quote source intact, so I don't know
to whom I should address this question, however...
Are you telling me that when I attach Pentax' own M42 to K-mount adapter
ring to my K-mount bodies, none of the M42 lenses I subsequently mount
will actually be able to focus to infinity?!
No. M42-mount has a smaller diameter than K-mount. Therefore a M42->K
adapter will fit inside the K-mount, leaving the register intact. A K->M42
adapter will not fit inside an M42-mount. The register is enlarged, so the
adapter functions as a small extension tube, ruïning infinity focus. The
Nikon to M42 probably has similar issues.
I was rather nonplused, but managed to ponder...I think that when such a
situation occurs, I don't think I attach any M42 mount lens specifically
to take scenics or other very long distance shots, nor did I blow any of
them up to 11X14" or beyond, so I guess I never noticed.
Nope, the problem never occured.
--
Regards, Lucas
