Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-10-2010, 08:09 PM   #1
Forum Member




Join Date: Jul 2008
Location: tokyo
Posts: 83
M42 lens trap, focus infinity?

Just got a 28mm f3.5 smc takumar and seem to be having problems focusing to infinity.

Also is it possible to use trap focus with this lens?

Any comments would be much appreciated.

03-10-2010, 08:37 PM   #2
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
QuoteOriginally posted by kiwao Quote
Just got a 28mm f3.5 smc takumar and seem to be having problems focusing to infinity.

Also is it possible to use trap focus with this lens?

Any comments would be much appreciated.
Is this the K-mount lens? If it does not focus to infinity, it could mean that the focusing ring is not aligned properly. With most MF lens, you can re-adjust, but that would mean that you have to disassemble the front lens element and loosen the screws and then calibrate that again. If you are not comfortable with that, perhaps, you should get it fixed in the repair shop.

How far can you still focus with this lens? You may still use it without get fixing if you can focus quite a distant. I am not sure if this has anything to do with trap focus, perhaps, someone else can chime in.
03-10-2010, 09:20 PM   #3
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,838
What kind of M42 adapter do you have? The cheap ones with a wide rim don't allow infinity focus because they change the registration distance. To focus to infinity you need an adapter that fits entirely inside the camera, like the Pentax adapter.

Trap focus does not work with M42 lenses.
03-10-2010, 09:36 PM   #4
Forum Member




Join Date: Jul 2008
Location: tokyo
Posts: 83
Original Poster
Thanks for the quick replies. I'll get the pentax adaptor and forget about trap focus.

03-10-2010, 10:22 PM   #5
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by boriscleto Quote
Trap focus does not work with M42 lenses.
Hmmm (gripe groan mutter bitch whine)... I wish that was documented in the manual. Here I've been shooting adapted M42's and wondering why it didn't work. So I just read the above and tried shots with an A-type Focal 135/2.8, M-type Takumar 135/2.5, and M42 Enna 135/3.5. Sure enough, the Focal and Tak both trap and the Enna doesn't. (The Enna sure is crisp though.) Try out a few other lenses and yup, same results. Even the M-type Zenitar 16/2.8 -- I guess I was lucky to score that one with a K-mount. BUT WHY WASN"T THIS DOCUMENTED!?!?!?!

Addendum: I'm guessing the K20D wants to see the little aperture flag that's on K-mount lenses and isn't on adapters -- not on M42-PK, nor T1- or T2-PK, nor any others I recall. Is a little fakery possible? Maybe replace a T2-PK with a cut-down K-mount stop-down macro tube? Or just superglue an aperture flag to an adapted lens base? Need the flag be actually connected and operational? Has anyone here tried any of this?

ANSWER: Aha, now I see! It's the old short-out-the-contacts-with-tinfoil trick! And a flanged not-infinity-focus adapter will short the contacts, whilst an Official Pentax or Bowers-type won't.

Last edited by RioRico; 03-11-2010 at 01:56 AM. Reason: addendum & answer
03-11-2010, 02:56 AM   #6
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
The hardware store has sticky back aluminum tape used to repair heating ducts. Put a bit on the base of your m42 lens to short out the data pin (closest to 6 o'clock.) Or scrape some paint off the lens base to short the contact.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
focus, k-mount, lens, m42 lens, pentax lens, slr lens, trap
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
infinity focus adjustment on M42 lenses Lowell Goudge Pentax SLR Lens Discussion 11 08-20-2009 01:49 PM
M42 Adapter: Can this type focus infinity? jocko_nc Pentax SLR Lens Discussion 6 05-08-2009 05:58 AM
Trap focus m42 Transit Pentax DSLR Discussion 5 01-12-2009 01:07 PM
For Sale - Sold: Genuine Pentax M42 adapter - allows infinity focus Finn Sold Items 1 04-05-2007 07:22 PM



All times are GMT -7. The time now is 03:31 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top