Trouble focusing screw mount lenses on *ist DL

[jonfuss]

I have been using a *ist DL for a few months, with both auto and manual K-

mount lenses of various vintages, with great success using the tips found on

this forum. I picked up a couple of M42 screw mount lenses and adapters, and

have had no success using them due to a focus issue.

 

They won't focus to infinity. I screw the adapter onto the lens, attach the

lens/adapter combo to the body, and I find that the lens is slightly turned to

the right (looking down at it). That is, the center marker for the aperture is

to the right of center.

 

Then when I focus, the ring reaches infinity (and stops) before infinity comes

into focus. Stopping down several stops brings infinity into focus via the

depth of field effect.

 

I bought the adapters new, and the lenses from reputable companies. The lenses

in question are a Vivitar 28mm f/2.5 and a Pentax SMC Takumar 135mm f/3.5.

 

I think I'm missing something fundamental here. Any help would be greatly

appreciated.

[skjeggestad]

I have heard that some third party adapters messes up infinity focus because they leave the lens to far out so as to increase the register distance. The original Pentax adapters do not have this problem. That is what I have heard anyway.

[Jochen_S]

Get a comparably sharp edged ruler and check if the flange of the adapters you're using extrude over your cameras mount, by holding a strong light source behind the ruler for example. If so either send them back or grind tehem down (outside the camera!) until they fit.

 

Does pressing the naked screwmount lens set to infinity at wide open by hand into the k-mount hole of the camera provide a picture sharp at infinity or beyond it?

 

If so: grinding stones are cheap... If not I'd send camera and Takumar to Pentax and ask for help, especially if there's remaining warranty.

[mawz]

Is the adaptor flush with the lens mount or does it have a lip that fits over the camera's lens mount? If the latter, the adaptor will never acheive infinity focus and you need to get a proper adaptor.

 

I also recommend that you insert the adaptor into the mount then mount the lens to the adaptor. That way you can be sure the adaptor is mounted correctly.

[john carter]

I have a DL and a PENTAX adapter. My screw mounts work to infinity, no problems. I also use my screw mounts on a K mount film Pentax camera again no problems with the PENTAX mount.

[jonfuss]

Looks like I got taken for a ride on the adapters. Upon examining the listing again, knowing what you have told me, I see that it says (in small print) that focus range is "limited." At the time I took that to mean that the auto focus wouldn't work, but now I know better. Geez. There goes $45 on adapters out the window.

 

Anybody want the lenses? I'm not going to spend any more on this little project.

[gib]

great lenses, i would get a better adapter, i have used an adapter on a PZ-1 for m42 Pentax lenses and it worked fine.

[jonfuss]

Thanks for bringing me back to reality. Does anyone have experience with Pentax vs. third party adapters, and any ideas on where to shop around for them?

 

Thanks again for all your input!

[gib]

I bought mine from Henry's Cameras in Toronto - they have an ebay online store and may have some adapters listed, not sure.

 

 

I found it best to remove the adapter and lens from the PZ-1 body. When I took the lens off the adapter it was hard to get the adapter out of the body. You dont want to super tighten the lens on the adapter either.

[eugene_lepekhin]

Jonathan, welcome to our club! I've experienced a lot of troubles trying to use various M42 lenses and a multitude of adaptors on my istDL.

As far as I see it, the problem lays in different shape of the M42 lens' back - some of them are completely flat (like old Takumars), some have a little "step" around the thread (like new Voigtlander or Zeiss ZS). Usually, for the lens with "flat rear", Pentax M42/K adaptor (Pentax-made, not the cheap one from local store or eBay) works fine with any Pentax K-bayonet camera. Other adaptors may have a "lip" wich sits on top ot the bayonet - they'll never have an infitity focus! Others may sit flush inside the bayonet (this is the right way) but might be too tight or too flimsy in the bayonet - and there is a zillion of wrong adaptors around.

The best way (at least for Takumar-like lenses) - buy yourself a Pentax-made "Adaptor B" and enjoy the real treasures of screw-mount optics!

Also, rumor has it that the new Zeiss ZS lenses go OK with Pentax-made adaptors. New Voigtlanders SL, though, is a completely different story.

[cymen_vig]

You can find the original Pentax M42 adapter on eBay occasionally. That is the fastest way to find it if you can't get it locally. Otherwise, go to:

 

http://www.pentaximaging.com/

Purchase Our Products

Shop Online

SLR Accessories->Teleconverters/Mount Adapters

Mount Adapter B

 

$30 plus shipping ($6.95 in US?)

 

Note that Pentax USA gets shipments in every month or so and sends them out so be prepared to wait. I was lucky and found one on eBay. I've seen a couple more on there but expect to pay as much as a brand new one from Pentax. The Kalt brand from BHPhotoVideo.com is also supposed to work but it isn't made as well as the Pentax one.