Kern Switar 25mm 1.4 on Olympus E-P2 : focus problem

LyleBright · Joined: 05 Jun 2018 Posts: 22

Hello. I just got this lens, mounted it in an adaptor, and began to use it. It works fine at close focus and makes a nice (quite nice) image, but for reasons I do not understand does not allow focus beyond 4 feet out.

It only focuses between about 1' and 2-1/2

It does seem to me that the lens sits much further down into the Fotiodox c-mount adaptor than my other lenses of the same sort (Cooke Kinic 25mm and a Dallmeyer 25mm)

The lens is acting like a macro lens.

Questions:

1) Any insight into this?
2) Is there another sort of c-mount adaptor that I should use?
3) Is the lens simply defective due to some internal slippage? (I am guessing here).

Your help is much appreciated.

calvin83 · Joined: 12 Apr 2009 Posts: 7554 Location: Hong Kong

If your lens is not the RX version, you may need to do some modification to shorten rear part to get infinity. Check the link below on http://oldlensclub.hk/viewtopic.php?t=1526

http://oldlensclub.hk/download/file.php?id=7222&sid=391faac7d88c04f7cabc9693eb7d9246&mode=view

LyleBright · Joined: 05 Jun 2018 Posts: 22

Thanks you! I see now that I need the RX model. Shame, this lens is in perfect condition.

Thanks for setting me straight.

kds315* · Expire: 2021-03-09

paulhofseth · Expire: 2018-06-28

I have not consulted the Kern/Paillard sources, but seem to recall that it was when the reflex was introduced that the RX lens was recalculated to compensate for the splitting prism. At the same time the flange distance was changed.

Hence a normal Kern (untoutched by amateur cleaners and restorers) should behave properly if allowed to do so by the adapter. According to Kern(?) or Paillard(?) the differences in performance if using the wrong calculation type lens will mainly show up at large openings.

p.