[kiwao]

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.

[aleonx3]

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.

[boriscleto]

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.

[kiwao]

Thanks for the quick replies. I'll get the pentax adaptor and forget about trap focus.

[RioRico]

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.

[newarts]

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.