p.1 #1 · Fixing messed up infinity focus in a vintage lens
Experts/Gurus, I bought a vintage lens (Yashica Yashinon 5cm f2) and only to find that somebody had messed up it's infinity focus. I am assuming they tried to "service" the lens and as part of that messed up the infinity focus.
Is there anyway to recalibrate the infinity focus. I understand the lens need to be ripped apart to do that, but my question is how difficult is that process? I have done this with another vintage lens (not recalibrating, but taking it apart and cleaning) and would not mind taking that road again, but this one seems to be a completely different beast with a cocking lever etc. and with the aperture ring in the front.
Any help, if somebody had been through this path in the past is highly appreciated. I am attacking a photo for reference.
Sreedhar.
Jan 27, 2026 at 03:24 PM
AmbientMike Offline • • • • • • [X]
p.1 #2 · Fixing messed up infinity focus in a vintage lens
Id try looking at the back and see if maybe someone took a rear element out putting it back in upside down. A lot of times you can see marks on the screws if people took it apart and didn't really know what they're doing
p.1 #3 · Fixing messed up infinity focus in a vintage lens
Steve, thank you for your response and an interesting thought. I was only thinking from the incorrect repositioning of the focus helicoid, but you provided another perspective. The lens has definitely been serviced based on the markings. It appears that it is in the correct way (the element closest to the sensor). However, you have a very valid point. What I am thinking is there are some adapters that come with helicoids. I want to try one of them (after a mod on them by somehow reducing it's thickness by 1mm or so by filing it) and see if it solves the issue. I am hopeful that should work as it makes it that much closer to the sensor. I have ordered an adaptor and waiting for it now, so that I can do a mod on that rather than the lens itself.
Jan 28, 2026 at 08:04 AM
AmbientMike Offline • • • • • • [X]
p.1 #4 · Fixing messed up infinity focus in a vintage lens
guywithgas wrote:
Steve, thank you for your response and an interesting thought. I was only thinking from the incorrect repositioning of the focus helicoid, but you provided another perspective. The lens has definitely been serviced based on the markings. It appears that it is in the correct way (the element closest to the sensor). However, you have a very valid point. What I am thinking is there are some adapters that come with helicoids. I want to try one of them (after a mod on them by somehow reducing it's thickness by 1mm or so by filing it) and see if it solves the issue. I am hopeful that should work as it makes it that much closer to the sensor. I have ordered an adaptor and waiting for it now, so that I can do a mod on that rather than the lens itself. ...Show more →
You're welcome, another reason I suggested looking for marks is that you could go in where they did, and maybe be able to fix the part that got messed up.
Does it get fairly close to infinity? A lot of adapters are thin to ensure infinity focus
p.1 #5 · Fixing messed up infinity focus in a vintage lens
There are many different lens designs. Some have easily accessible set screws on the outer barrel that you can loosen to adjust the helicoid. They might be underneath rubber focus rings. Other lenses require disassembly and might use either shims or concentric threaded rings to move the point of focus.
p.1 #6 · Fixing messed up infinity focus in a vintage lens
AmbientMike wrote:
You're welcome, another reason I suggested looking for marks is that you could go in where they did, and maybe be able to fix the part that got messed up.
Does it get fairly close to infinity? A lot of adapters are thin to ensure infinity focus
Yes, it does fairly close to infinity. By infinity I mean a building about 20 - 25 meters away. Any further, it gets worse. Having said that I checked the same adapter with other M42 lenses (including one that I personally dismantled and reassembled after helicoid regreasing), they all work. And that is how I came to a conclusion that the reassembly of the lens is what caused the issue. Earlier I had a thought in mind that film era lenses are calibrated a bit differently. But as far as my knowledge and understanding goes, they are usually focused beyond infinity (to allow the temperature changes etc.). But this is the other way round.
I am trying with other adapter (waiting for it to arrive) to eliminate all possibilities and zero in on to the fact that, in fact it the lens and not the adapter(s).
Price we pay when we buy things online . I guess comes with the territory?
p.1 #7 · Fixing messed up infinity focus in a vintage lens
jeffbuzz wrote:
There are many different lens designs. Some have easily accessible set screws on the outer barrel that you can loosen to adjust the helicoid. They might be underneath rubber focus rings. Other lenses require disassembly and might use either shims or concentric threaded rings to move the point of focus.
Agreed, but this from 60s. All metal and no rubber. I can only see (and perhaps understand) only once I unmount the lens to a certain degree. The glass is so clean for the age of the lens, that I am a bit skeptical about that approach. Will try different adapters first and see if one of them is better designed (to focus beyond infinity) and that allows me to focus to infinity.
p.1 #9 · Fixing messed up infinity focus in a vintage lens
Likely the helicoid was separated and is off by one or two if someone messed it up on reassembly. I don’t know anything about that particular lens’ construction. It may take trial and error to move the helicoid one thread then reassemble and test repeating until infinity is correct.
On some Nikon lenses I’ve worked on the hard stops were built into the focus ring but it was possible to adjust the focus ring attachment to the helicoid to tune infinity.
p.1 #10 · Fixing messed up infinity focus in a vintage lens
jpelt78 wrote:
Likely the helicoid was separated and is off by one or two if someone messed it up on reassembly. I don’t know anything about that particular lens’ construction. It may take trial and error to move the helicoid one thread then reassemble and test repeating until infinity is correct.
On some Nikon lenses I’ve worked on the hard stops were built into the focus ring but it was possible to adjust the focus ring attachment to the helicoid to tune infinity.
I do not have a lot of experience in taking apart and putting back of the legacy lenses, but I do agree with you on the approach. I don't think I have any other choice but take it down and go on the trial and error method. Some lenses do have infinity adjusters (ex: Mamiya-Sekor 55mm f1.4 has that arrangement) where you don't have to mess around a lot but adjust the stopper to achieve infinity focus. I searched down the rabbit hole of internet & YouTube and could not find the information needed for disassembly of this specific lens. But found something close (of disassembly of a an auto Takumar that has similar cocking lever mechanism for aperture). I may have to take the risk myself go down that route. But I am trying to find a lens of same model for parts to experiment first.
Feb 03, 2026 at 10:50 AM
AmbientMike Offline • • • • • • [X]
p.1 #11 · Fixing messed up infinity focus in a vintage lens
I picked up a sub $20 50/2 several years ago off ebay. I alreadu had m42 extension tubes ($10.95, keh.) I had fun using it as a primary lens , infinity fine but also getting really close with the extension tubes on m4/3
p.1 #12 · Fixing messed up infinity focus in a vintage lens
AmbientMike wrote:
I picked up a sub $20 50/2 several years ago off ebay. I alreadu had m42 extension tubes ($10.95, keh.) I had fun using it as a primary lens , infinity fine but also getting really close with the extension tubes on m4/3
So you might just go with it and get some tubes.
Steve, I agree a 100%. However, I did go the route of a helicoid adapter; that serves the purpose of both M42 to Nikon adaption as well as close up photography.
p.1 #13 · Fixing messed up infinity focus in a vintage lens
I take it the registration marks are close but not quite? Meaning at infinity (on the lens) you’re okay to 20-25m? And at MFD you’re within a half meter or so? If that’s the case I’ll argue it’s likely not the helicoid. When those are off the focus distance vs focus scale is completely off. And the hard part there is you have no way of knowing where it needs to be if they didn’t make the correct reassembly point so you might need to reassemble 3-5 times to get it. But if it’s close as assumed above then you likely won’t gain much by separating the helicoid.
p.1 #14 · Fixing messed up infinity focus in a vintage lens
AdaptedLenses wrote:
I take it the registration marks are close but not quite? Meaning at infinity (on the lens) you’re okay to 20-25m? And at MFD you’re within a half meter or so? If that’s the case I’ll argue it’s likely not the helicoid. When those are off the focus distance vs focus scale is completely off. And the hard part there is you have no way of knowing where it needs to be if they didn’t make the correct reassembly point so you might need to reassemble 3-5 times to get it. But if it’s close as assumed above then you likely won’t gain much by separating the helicoid. ...Show more →
The MFD is fine. The farthest I could focus is around 7-8 m. Not beyond that. Honestly, I do not know how to deal with it yet. Perhaps try take it out and put it back (the focus is stiff as well). It definitely needs a regreasing. As the glass is clean, at least I will give that a go. Worst case scenario, I may not be able to fix the infinity focus, and that is not working anyway. But at least I will get the focus ring smoothened.
p.1 #15 · Fixing messed up infinity focus in a vintage lens
So the symbol to focus distance is okay, but it hits a stop somewhere around 7-8m. That’s probably a good thing. Don’t seperate helicoid, you’ll need to pull the optical block and inspect the aperture mechanisms. They frequently have a mechanical interface with the rest of the lens that lets aputure function regardless of lens focus. Looks like something is out of place and hitting. While open you can also focus to mfd and clean some threads (maybe- they aren’t always exposed) but if so they can help.
guywithgas wrote:
The MFD is fine. The farthest I could focus is around 7-8 m. Not beyond that. Honestly, I do not know how to deal with it yet. Perhaps try take it out and put it back (the focus is stiff as well). It definitely needs a regreasing. As the glass is clean, at least I will give that a go. Worst case scenario, I may not be able to fix the infinity focus, and that is not working anyway. But at least I will get the focus ring smoothened.
p.1 #16 · Fixing messed up infinity focus in a vintage lens
AdaptedLenses wrote:
So the symbol to focus distance is okay, but it hits a stop somewhere around 7-8m. That’s probably a good thing. Don’t seperate helicoid, you’ll need to pull the optical block and inspect the aperture mechanisms. They frequently have a mechanical interface with the rest of the lens that lets aputure function regardless of lens focus. Looks like something is out of place and hitting. While open you can also focus to mfd and clean some threads (maybe- they aren’t always exposed) but if so they can help.
Thank you very much. If I understand correctly, the aperture mechanism (in this case any minor misalignment of it) is blocking the last leg of focus ring. Gotcha, I will look for clues there. My thinking of disassembling the helicoid and regreasing it goes on the same lines. I thought the grease might have hardened at the last leg of focus ring and that was stopping it. Never thought of other parts of the lens coupld be doing the same. At least you gave me some ideas, thanks again.
p.1 #17 · Fixing messed up infinity focus in a vintage lens
And it could be grease but that won’t (usually) be a hard stop. But infinity is the most compact position of the lens, close focus is the longest. Looks like the aperture ring is on the front while the iris is usually behind the middle somewhere, so there’s a leg that runs down the helicoid to the iris. If it’s out of position it’ll hit as it retracts and basically stop the lens from retracting further. Depending on stop down mechanisms etc. there can be more than 1 leg that interfaces. I’m not as familiar with Yashica in particular (different brands seems to have different general design ideas) but that should give you a starting point. But again if 7-8m is accurate with plane of focus then don’t separate the helicoid for sure, it’s good.
guywithgas wrote:
Thank you very much. If I understand correctly, the aperture mechanism (in this case any minor misalignment of it) is blocking the last leg of focus ring. Gotcha, I will look for clues there. My thinking of disassembling the helicoid and regreasing it goes on the same lines. I thought the grease might have hardened at the last leg of focus ring and that was stopping it. Never thought of other parts of the lens coupld be doing the same. At least you gave me some ideas, thanks again.
p.1 #18 · Fixing messed up infinity focus in a vintage lens
Thanks once again. I'm definitely getting a mental picture of what you are talking about. I'll try to open the optical elements and give a deeper look at the aperture mechanism this weekend. Hopefully, I should be in a better position once I open the lens.
AdaptedLenses wrote:
And it could be grease but that won’t (usually) be a hard stop. But infinity is the most compact position of the lens, close focus is the longest. Looks like the aperture ring is on the front while the iris is usually behind the middle somewhere, so there’s a leg that runs down the helicoid to the iris. If it’s out of position it’ll hit as it retracts and basically stop the lens from retracting further. Depending on stop down mechanisms etc. there can be more than 1 leg that interfaces. I’m not as familiar with Yashica in particular (different brands seems to have different general design ideas) but that should give you a starting point. But again if 7-8m is accurate with plane of focus then don’t separate the helicoid for sure, it’s good.
p.1 #19 · Fixing messed up infinity focus in a vintage lens
well...well...well. Finally I was able to figure out how to make the infinity work on this lens.
First, I ripped it apart to figure out what kind of mechanism it uses. Its a single screw stopper for infinity. So, I did not have any leverage ( I was hoping it would be multiple pins that I can work around with, but not). After a lot of trial and error I was able to make the focus mechanism work and reassemble the lens. It made only the focus ring smoother but the infinity focus was still a problem.
After deciding I can't make it work, took a different approach. Found 3 different adapters to make one adapter. T2 to Nikon Z adapter and a couple of M42 - T2 adapters to make all 3 of them to be a single adapter. That did the trick. Of course, there was a bit of luck in this approach. The total thickness of all 3 adapters brought the flange distance in the range to make the infinity focus work (I was hoping it would and that is what is the luck part). Only caveat is, it was not perfect, the MFD was extended a little bit, but I can live with that.
Posting the solution here, may be this will give somebody some ideas for their problems (or not)!
. I guess comes with the territory?
