Super Takumar 55/1.8 infinity focus adjustment

okacat · Joined: 21 Feb 2016 Posts: 5

Hello!

I'm using a Sony A5100 with and M42 adapter to use vintage lenses. Up until now, I've had no problem with lenses not focusing to infinity, I have a Helios 2, a 35mm Pentax and another 135mm. All are M42, so the adapter is not to blame. Recently, I bought a Super Takumar 55mm f1.8 off Ebay which wouldn't focus to infinity. First I though it might be a problem with the aperture pin, since it doesn't come flush with the body of the camera when it's pressed in as far as it will go. I even went as far that I filed the pin down to just a stub, until I figured out that was not the actual problem. There was still room between the pin and the adapter when the lens was screwed on completely, but still no infinity focus. After reading around forums a bit I found this guide: k10dpentax.blogspot.si/2008/05/fixing-infinite-focus-on-super-takumar.html

I gave it a shot, had no problem following it, but I soon found out that there was no more room for adjustment. The focus came to a stop, it appears the screw thread of the focus (I believe it's called a helicoidal) ended. Even if I unscrewed the 3 screws holding the focus grip and removed the grip completely, I couldn't turn the focus anymore towards infinity. I find this weird, since I'm sure the lens should focus to infinity on my setup, since all the other M42 lenses do. Is there something else that I can attempt to do to move the optics further back, thus getting infinity focus?

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Helicoid on a tak should have suffiecient room for such an adjustment. But you know that with the focusing ring of you need to rotate not the helicoid itself, but the ring it sits in, right? It even has a special hole where you can insert a tool to help it move. That does not work? Any indication that the lens had been opened previously?

okacat · Joined: 21 Feb 2016 Posts: 5

You mean the brass part that the focusing grip is attached to with three screws? I was rotating that, if I rotate it all the way towards minimum focus distance the helicoid comes out, if I rotate it the other way, towards infinite focus, it get's stuck when it the helicoid itself (the part that the optic block is screwed in) hits the aperture mechanism at the bottom, focus is still not at infinity when that happens. I'm not sure if it has been opened before, but I would say that it was since the operation of focus was very smooth, and there was no old grease inside. Sorry if my terms for the parts are incorrect, I can post some photos later to clarify.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Quality of focusing is not in indication of it being opened. Many takumars focus exceptionally smooth even after 40-50 years. Rather, was there any dirt and grime under the name ring when you unscrewed it? Were the focus adjustment screws secured with lacquer?
I mean it's possible that someone did not assemble it correctly but in honesty I am not seeing it as very probable.

okacat · Joined: 21 Feb 2016 Posts: 5

Alright, wasn't aware of that, thanks. The screws weren't lacquered as far as I remember, there wasn't much grime under the name ring. Only the brass part has dirt spots over the top part where the screws are attached.

visualopsins · Expire: 2025-04-11

Last person in couldn't find the correct helical threads...

The helical needs to be screwed on the correct threads to achieve infinity focus.

The (fine) infinity focus adjustment has been lost, so you'll need to add the step of trying to adjust focus adjustment after each helical start position try...

okacat · Joined: 21 Feb 2016 Posts: 5

Is it surely the helicoidals? If so I would be very thankful if you could elaborate on the steps to take to try to adjust it back correctly.

Here's why I'm not sure that's the problem, even though it would be weird if it was something else. Posting some pictures for clarity.

#1

The lens with the focusing grip/ring removed. I was turning the brass part by hand, there is a two directional arrow next to it.

#2

Brass part rotated to about halfway towards minimum focus distance (the whole optics block moves further out). 1 is the brass part that I rotated, 2 is the helicoidal that holds the optics block and 3 is the optics block.

#3

Optics block removed from the helicoidal, so I was able to better see what was going on.

#4

Close up inside the helicoidal. As you can see the helicoidal hits the aperature mechanism causing it to stop. The lens is not at infinite focus when this happens, this is the reason that I'm so confused, since I don't see how adjusting the helicoidals differently would allow the lens to move even further back thus achieving infinite focus.

I would be very glad if somebody has a solution to this. Thank you.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

If I have time I'll pop one open tomorrow to look at the mechanism. Is that Super of SMC?

okacat · Joined: 21 Feb 2016 Posts: 5

That would be really helpful, thank you. It's a Super Takumar 1.8/55.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

I am having trouble locating a proper tak, even though I know I must have a few of them.

Kinosaur · Joined: 15 Dec 2016 Posts: 11

Hi

I realise this was all quite a long time ago, but was the issue ever resolved? I'm looking for clues as to the best way to proceed with an Auto Takumar 35 2.3
and looking at the pictures of this lens there are a couple of slight similarities.

karthikrr · Joined: 04 Jun 2019 Posts: 23

Not that I like reviving dead threads, but I just resolved a similar problem on my copy and found this thread while looking for help. So, maybe this helps the next person.

In my case, the aperture block was not seated properly, so when going towards mfd, the aperture control assembly would slip out, and then when going back towards infinity, it would hit the arm and stop well short.

The solution was to remove front optical block, unscrew the aperture retainer ring, then remove aperture and rotate it a little bit till it found the groove and slotted in deeper than it had been. The locking thread should be able to screw in flush with the barrel around it. Replace optical block and name ring and everything was working again.

Note that this was significantly easier to do with the entire lens disassembled rather than just the front optics. It's doable, but to get the mechanism to the right place, a fair bit of trial and error might be needed.