On Oct 4, 2005, at 10:41 AM, keith_w wrote:
M42 and K-bayonet have the same register...
Lens mount body flange-to-film plane measurement?
Yes. That's what a camera's register is defined to be.
here used to be a K-to-M42 adapter that did allow infinity focus. It
contained one or more optical elements to make this work. ...
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?!
The direction of adaptation is important:
- M42 to K-mount adapter mounts a thread mount Pentax lens onto a K-
mount body. Same register, thread mount fits inside the K-mount,
perfect infinity focus.
- K-mount to M42 adapter would have to mount a larger diameter lens
onto the body with the same register, which will *have* to lose
infinity focus or require optics to compensate for the different
distance the lens will sit from the imaging plane.
- K-mount and Nikon mount are very close in both diameter and
register, so it's difficult to make an adapter that would take either
series lens and allows infinity focus.
- M42 is again smaller diameter and the same register as K-mount, so
it's impossible to make an adapter for Nikon without optics that
would allow infinity focus.
For more information, see:
http://www.a1.nl/phomepag/markerink/mounts.htm
Godfrey
