Nikon manual focus lens infinity adjustment

Nikanon · Jul 25, 2022

Hello,

This is not a problem i have ever encountered before as I am not a big user of Nikon 35mm SLR's until recently, but I noticed some of my lenses align perfectly at infinity with no microprism distortion or rangefinder split misalignment, and others do not despite having never done much to the lenses in question. My brand new 40mm f2 Voigtlander Ultron SL-IIs aligns perfectly while my 35mm f2 Ai does not quite get to infinity. Any idea on how to adjust this lens so it reaches infinity? Just when you think you've escaped alignment issues by putting down the Leica for a little...

reddesert · Jul 25, 2022

It should reach infinity. They all should. IME, older manual focus SLR lenses are generally accurate at the infinity stop and only some AF lenses will focus past infinity. This assumes your SLR focus screen is itself properly positioned.

I had a Nikon 35mm/2 pre-AI that was fairly well used and wouldn't quite reach infinity. The front part of the barrel had a noticeable small wobble. IIRC, I took apart just enough of the lens (removed the outer focus ring) to reach a few small screws in the side of the front barrel that were loose and tightened them. Now the lens reaches infinity fine. There are similar procedures for other lenses (many are shown on Richard Haw's Nikon lens repair pages), but if nothing's obviously loose then you shouldn't really need to do this. I would also check with another SLR and/or check that your focusing screen is fully seated, first.

Nikanon · Jul 25, 2022

reddesert said:
It should reach infinity. They all should. IME, older manual focus SLR lenses are generally accurate at the infinity stop and only some AF lenses will focus past infinity. This assumes your SLR focus screen is itself properly positioned.

I had a Nikon 35mm/2 pre-AI that was fairly well used and wouldn't quite reach infinity. The front part of the barrel had a noticeable small wobble. IIRC, I took apart just enough of the lens (removed the outer focus ring) to reach a few small screws in the side of the front barrel that were loose and tightened them. Now the lens reaches infinity fine. There are similar procedures for other lenses (many are shown on Richard Haw's Nikon lens repair pages), but if nothing's obviously loose then you shouldn't really need to do this. I would also check with another SLR and/or check that your focusing screen is fully seated, first.

Based on the brand new Voigtlander 40 lining up perfectly and checking the screens in all three of my nikons to be seated fine, I believe the cameras not to be the problem here. I know of the screws on the 35mm f2, but they are tight and i am not sure what is needed to be done in this area to adjust the infinity stop. The lens does not focus to infinity on my F3, FM2 and FE2. The voigtlander 40 does on all three

cjbecker · Jul 25, 2022

Its been a while for me having too adjust the infinity focus on a ai/ais lens, but if you remove the lens mount, i think the adjustment is made from the infinity stop at that point. But it takes a few tries, cause you have to adjust it, put the lens back together and test, then repeat till perfect.

Nikanon · Jul 25, 2022

cjbecker said:
Its been a while for me having too adjust the infinity focus on a ai/ais lens, but if you remove the lens mount, i think the adjustment is made from the infinity stop at that point. But it takes a few tries, cause you have to adjust it, put the lens back together and test, then repeat till perfect.

i've seen this mentioned a lot but im having a hard time determining what exactly needs to be done, what is adjusted exactly and how?

beemermark · Jul 25, 2022

Are the shots with the Nikon lens sharp. If they are then don't loss sleep over it.

reddesert · Jul 25, 2022

Richard Haw has a full tear down of the 35/2 AI at https://richardhaw.com/2018/07/28/repair-nikkor-35mm-f-2-ai/

I think he gets to the physical infinity stop after disassembling the helicoid, and my feeling is that unless you are extremely confident it is best not to disassemble the helicoid, as they are difficult to get back together properly. I would look first at making sure the optical block is actually together right, the mounting of the optical block into the focusing assembly, and whether the outer focusing ring is in the correct position.

r_a_feldman · Jul 26, 2022

This might not be the approved method but when I had a Nikkor lens that focused beyond infinity, I removed the lens mount and reassembled it with a thin shim between the mount and the lens body. I have used 0.005” mylar drafting film and thin brass from K&S Metals (you can buy a pack with 0.001”, 0.002”, 0.003” and 0.005” sheets). The mylar is easier to cut than the brass. It was trial and error to determine how thick the shim should be. I needed 0.007” for that particular lens.

Nikanon · Jul 27, 2022

reddesert said:
Richard Haw has a full tear down of the 35/2 AI at https://richardhaw.com/2018/07/28/repair-nikkor-35mm-f-2-ai/

I think he gets to the physical infinity stop after disassembling the helicoid, and my feeling is that unless you are extremely confident it is best not to disassemble the helicoid, as they are difficult to get back together properly. I would look first at making sure the optical block is actually together right, the mounting of the optical block into the focusing assembly, and whether the outer focusing ring is in the correct position.

I’ve taken a look at this. Taken out the optical block and gotten it back in, it sits only it one spot where the a small screw hole lines up so it can’t be that.

Nikanon · Jul 27, 2022

r_a_feldman said:
This might not be the approved method but when I had a Nikkor lens that focused beyond infinity, I removed the lens mount and reassembled it with a thin shim between the mount and the lens body. I have used 0.005” mylar drafting film and thin brass from K&S Metals (you can buy a pack with 0.001”, 0.002”, 0.003” and 0.005” sheets). The mylar is easier to cut than the brass. It was trial and error to determine how thick the shim should be. I needed 0.007” for that particular lens.

Oh boy, glad it worked for you! I just want the lens to function properly on its own as was designed

Nikanon · Jul 27, 2022

beemermark said:
Are the shots with the Nikon lens sharp. If they are then don't loss sleep over it.

They are at distances closer than infinity that can be aligned properly in the viewfinder. At infinity it is not quite sharp

guangong · Jul 27, 2022

Nikanon said:
They are at distances closer than infinity that can be aligned properly in the viewfinder. At infinity it is not quite sharp

To me, this doesn’t seem to make sense. All the optics I remember came from my high school physics classes from 70+ years ago, so I could be wrong.

ic-racer · Jul 27, 2022

Nikanon, did you figure it out. I have not set infinity focus on a Nikon lens, but other similar. Did you see this, which is I believe the adjustment on your lens?
For sure adjust it for infinity and let the other distances fall where they may.
FYI: in all the years I have been taking cameras and lenses apart, only a few times was the lens infinity stop out of adjustment. More frequently it was a film flatness issue or a problem with the mirror adjustment. Usually the lens mount, lens infinity stop, film gate and pentaprism are fixed pretty well. The mirror, flapping up and down, can be a real source of focus errors if it shifts at all from the day it was built. For example in the linked article he states the ring below was glued in place not to move.

reddesert · Jul 27, 2022

guangong said:
To me, this doesn’t seem to make sense. All the optics I remember came from my high school physics classes from 70+ years ago, so I could be wrong.

The OP is saying that the lens doesn't reach infinity focus, but it can be focused in the viewfinder at shorter distances (although then the marked distance scale on the focus ring would presumably be off).

There are about two ways this could happen, either the lens mount or focus helical are mechanically off, or the lens optics could be assembled wrongly to slightly increase the focal length. The latter is what was wrong with my lens when the front barrel was slightly loose.

beemermark · Jul 27, 2022

reddesert said:
The OP is saying that the lens doesn't reach infinity focus, but it can be focused in the viewfinder at shorter distances (although then the marked distance scale on the focus ring would presumably be off).

There are about two ways this could happen, either the lens mount or focus helical are mechanically off, or the lens optics could be assembled wrongly to slightly increase the focal length. The latter is what was wrong with my lens when the front barrel was slightly loose.

Or maybe something else is wrong with the lens that is physically preventing it from focusing to infinity (not anything to do with the focus mechanism). I have never had a SLR lens focus problem with the image being sharp vs lens markings not agreeing with the focusing screen. Not sure if I'm clear but if the markings on the lens is rarely exact, but there are so many other things that can be wrong.

Nikanon · Jul 31, 2022

guangong said:
To me, this doesn’t seem to make sense. All the optics I remember came from my high school physics classes from 70+ years ago, so I could be wrong.

If you imagine the lens has a hard stop at which infinity is properly aligned and this infinity stop can be adjusted closer or further, the full range of focus being visually done through one lens unlike a rangefinder can still be able to be focused while the lens can’t quite reach infinity. That appears to be my issue

Nikanon · Jul 31, 2022

ic-racer said:
Nikanon, did you figure it out. I have not set infinity focus on a Nikon lens, but other similar. Did you see this, which is I believe the adjustment on your lens?
For sure adjust it for infinity and let the other distances fall where they may.
FYI: in all the years I have been taking cameras and lenses apart, only a few times was the lens infinity stop out of adjustment. More frequently it was a film flatness issue or a problem with the mirror adjustment. Usually the lens mount, lens infinity stop, film gate and pentaprism are fixed pretty well. The mirror, flapping up and down, can be a real source of focus errors if it shifts at all from the day it was built. For example in the linked article he states the ring below was glued in place not to move.
View attachment 311222

Is that ring supposed to be able to be turned to adjust an infinity stop? I have not figured this out yet. I attempted seeing if the mirror was the issue by wedging and depressing it, and the image plane just became tilted in either direction and seems even as it rests, I didn’t think that was the issue. I really believe it is the infinity stop issue because most of my other lenses focus to infinity perfectly on the same cameras , my 35mm f2 and 50mm f1.4 however do not but still make excellent pictures at distances closer than infinity

Nikanon · Jul 31, 2022

beemermark said:
Or maybe something else is wrong with the lens that is physically preventing it from focusing to infinity (not anything to do with the focus mechanism). I have never had a SLR lens focus problem with the image being sharp vs lens markings not agreeing with the focusing screen. Not sure if I'm clear but if the markings on the lens is rarely exact, but there are so many other things that can be wrong.

This has to do with the lens not visually focusing to infinity period, the lens does stop at the infinity mark but the microprisms and rangefinder do not quite make it to infinity alignment on objects over a mile away. I can confirm when focused and shot at infinity the pictures are not tack sharp but all closer visually focused objects render perfectly at their focused point.

Sirius Glass · Jul 31, 2022

If it was me, I would take the camera or send the camera and lens to a qualified camera repair person or center and have the problem corrected. I have had good work done by KEH.com. Get the camera and lens adjusted to work correctly so that you can go out and use it.

flavio81 · Aug 4, 2022

reddesert said:
Richard Haw's Nikon lens repair pages), but if nothing's obviously loose then you shouldn't really need to do this. I would also check with another SLR and/or check that your focusing screen is fully seated, first.

+1

Richard Haw's website is thorough and has all the information you need. Just make sure to READ the separate page on "how to work with helicoids" and to follow his advice carefully.

We're lucky to have Richard Haw's pages, even though he's a bit of a anti-Canon guy ... lol...

Also note that Richard Haw also has probably the best tests of classic Nikkor lenses out there.

Nikon manual focus lens infinity adjustment

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