following a response I posted in a thread, regarding changing the infinity focus on Kiron and Vivitar (by Kiron) lenses,
https://www.pentaxforums.com/forums/905419-post64.html
I was contacted by a forum member for information on how this was done, so I decided to post the instructions here.
the lenses in question are 24mm F2 vivitar (kiron) and 28 mm F2 Kiron wide angle lenses, that I converted from nikon AI and Minolta MD mounts respectively to K mount using the flanged M42 adaptor.
I don;t know whether approach this applies to other makers as well
On the outside of the lens barrel of the optical group, just below the filter threads, there is a small set screw in the side of the barrel.
this locks the outer cover of the barrel to the ring with the makers name on it, under the filter. This outer cover is just that, it is not part of the lens itself structurally, it is just a hollow tube.
see image 2 the set screw visible on the collar (removed from lens)
If you remove this one set screw, you can thread the outer collar off and see the 3 screws that hold the focusing ring to the focusing helix
look at image 3 bottom right inside the lens, just below and to the right of the
1:2 marking. The second is under the
A of wide angle
if you undo these screws slightly the focusing collar is now independant of the helix,
to set infinity,
- you tighten one screw a little, and focus to infinity, then
- slacken the screw, and
- turn the collar to the infinity mark and
- retighten, the focusing is set,
I have no idea how other makers do it.
Last edited by Lowell Goudge; 02-09-2010 at 01:28 PM.