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10-14-2021, 02:58 PM   #1
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Takumar 50mm f1.4 can't focus to infinity

I raised this issue in a thread about the Takumar 50mm lens, but at his recommendation, I'm raising it in the lrns forum.

I bought a 50mm Super Takumar F1.4. It seems in good condition, but won't focus to infinity on either a K3-3 or a KP, despite using a genuine Pentax 42mm adapter.

I returned it to the supplier, who tested it on a digital camera with the same result, but found that on a Pentax Spotmatic it was fine.

Can anyone explain this? I wondered if the lens has been "tweaked" to go on a Canon body and perhaps there's more latitude on the older Spotmatic?

10-14-2021, 03:21 PM   #2
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Flange distance is off. Is it under focusing at infinity?
If it perfect on the Spotmatic, then it is correct, but easy to re adjust infinity focus.
Removing the name ring should get you access to the three focus ring screws


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10-14-2021, 07:51 PM   #3
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Flange distance should be the same on screwmount camera and K-mount bodies, including DSLRs. So as long as the rear surface of the lens mount is flush with the front surface of the body mount it should focus the same at infinity between bodies.

If the lens focused at infinity in Live View and not in the viewfinder than the focusing screen distance needs to be adjusted - unlikely since it was off on two bodies.

Is the supplier using a genuine Pentax adapter?

The threads may be damaged preventing the lens from mounting flush with the adapter but the damage is in an area where it clears on the Spotmatic.
10-14-2021, 08:01 PM   #4
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I have several manual lenses that don't quite ficus to infinity on a PENTAX body.
I adjusted them to focus just a hair past infinity using Live view.
Unfortunately I have no experience adjusting any of the Takumar lenses.

10-14-2021, 08:24 PM   #5
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Several of my m42 lenses won't focus to infinity. Most importantly my Tak 50 1.4 and my Tak 35 f2.3. Meanwhile my cheap Petri 50 1.7 focuses to infinity perfectly.

In my opinion it's just an old lens and old lenses need adjustments sometimes.
10-18-2021, 08:06 AM   #6
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Can you turn the focus ring all the way to infinity? I've had problems with Takumars on generic M42 adapters. The lenses have a (AFAIK proprietary) tab at the rear to communicate the aperture setting to the camera. It's an extremely tight fit on most adapters and the tab might get ever so slightly bent towards the centre. This will block the rear element from extending. In particular I've had this problem with the same lens as you (SMC version).


Try putting the adapter on the lens (without the camera) and check if you can turn the focus ring to the infinity mark (to the hard stop). Also check if you can change the aperture focussed as far away as possible.
10-18-2021, 11:44 PM   #7
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Thank you to for your responses. At the moment, the lens is back with the supplier and I'm not at home, so I can't act on any of the suggestions. I'm hoping to get the lens back to me by the weekend, when I'm back home, so I can follow up on some ideas.

10-22-2021, 07:42 AM   #8
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Fixing infinity focus on the Super Takumar 50mm F1.4

I've received the lens back and now adjusted the infinity focus with the help of an excellent YouTube video - null - YouTube. from mikeno62. I found that the rubber bush from the drum securing bolt supplied with a washing machine was the perfect size to remove the lens label ring and I was fortunate that mine unscrewed very easily. Following the instructions in the video, I removed the three screws indicated and the front barrel - this exposes the screws holding the focusing ring. there's no need to remove these - just loosen them, with the focus set to infinity, then with the focus ring free, move the focus to something like 20m and tighten them back up. This allows the lens to be refocused to infinity. At this stage, i checked the lens on my KP and it focused on my test subject - a neighbour's chimney at about 100m, with a bit to spare. So, I then put the lens back together - all done!

It was clear from scratches around the screws behind the lens label ring, that someone had been in there before me, presumably to adjust the lens for a non-Pentax body. I'm still not sure why the modified lens apparently worked on a Spotmatic, but not on a DSLR.

Thanks to all for their advice.
10-22-2021, 08:56 AM   #9
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Good deal, enjoy!!


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