Nikon 105mm 2.5 infinity issues

[Joseph Bell]

Hello, kingly practitioners!

Recently I acquired a Nikon 105mm f2.5 AI lens, and it is sharp and quite lovely, but when I try to focus at infinity (for example on a building in the distance) the focus will not line up exactly at infinity, and I need to move the focal ring just slightly back in order to get the image in focus.

I find this somewhat irritating, as of course it would be nice to use the hard infinity stop! I wonder if this is a common problem and certainly I will welcome your insight!

Many sincere thanks
Joseph

PS I do hope I am explaining this properly. I find it very difficult to explain these things! But I'll keep trying!

 

[narsuitus]

I do not know if it is a common problem but I bought a 105mm f/2.5 AIS Nikkor that had a similar problem. I purchased it at a discount because of the problem. It cost me more to repair the lens than I paid for the lens.


Nikon 105mm Lenses by Narsuitus, on Flickr

 

[shutterfinger]

The common reasons I can think of are:
1. The focusing helical has slipped causing the lens to focus past infinity.
2. A "tech" set infinity at 100 to 500 feet assuming that it would be used at f8 or smaller aperture (frequently called good enough or close enough).
3. Someone had the front element out for cleaning and left out a .005 shim or similar.
4. The collimator used to calibrate the lens was out of calibration.

 

[KN4SMF]

Another plausible possibility. Somebody had disassembled the lens including the infinity stop and failed to tighten the screws holding down that stop. When the user focuses and hits the stop, it moves slightly. It would have been helpful if the poster had mentioned just how far it moves past infinity, measured with a ruler, or at least a good estimate. This would help to discount or not the possibility that somebody had disassembled the focus helicals and put it back together with wrong thread entry points.

 

[Mick Fagan]

I doubt there is anything wrong with the lens. With Nikkor lenses, many of them do go over infinity so that infinity can be obtained in extreme conditions. Think -40C or over 50C where things either reduce due to the cold, or expand due to the heat.

From memory, my Nikkor 105 f/2.5 is just like that. You only need to pull it back a fraction to get correct focus. I have a pair of Leica Ultravid binoculars, they also go ever so slightly over infinity and need to be pulled back.

I cannot check, as I'm overseas from home, but my Nikkor 180 ED f/2.8 and my Nikkor 300 ED f/4.5 do exactly the same.

Mick.

 

[Joseph Bell]

I do not know if it is a common problem but I bought a 105mm f/2.5 AIS Nikkor that had a similar problem. I purchased it at a discount because of the problem. It cost me more to repair the lens than I paid for the lens.


Nikon 105mm Lenses by Narsuitus, on Flickr

Thank you truly!

 

[Joseph Bell]

I doubt there is anything wrong with the lens. With Nikkor lenses, many of them do go over infinity so that infinity can be obtained in extreme conditions. Think -40C or over 50C where things either reduce due to the cold, or expand due to the heat.

From memory, my Nikkor 105 f/2.5 is just like that. You only need to pull it back a fraction to get correct focus. I have a pair of Leica Ultravid binoculars, they also go ever so slightly over infinity and need to be pulled back.

I cannot check, as I'm overseas from home, but my Nikkor 180 ED f/2.8 and my Nikkor 300 ED f/4.5 do exactly the same.

Mick.

Hello Mick. Many sincere thanks to you. I am grateful for your time and erudition, and my mind is set at ease!

 

[ic-racer]

You probably will never find a service manual for that. I know on my Zeiss lenses, many have similar infinity stop mechanisms, making collimation easier once one has done it a few times. All my Nikkors are auto focus, so I'm not even going to guess as to were the adjustment is on your lens.

 

[ic-racer]

Having posted the above, a 35 second internet search shows that, at least on the shorter manual focus Macro Nikkors, the focus ring is attached to the helicoid by 3 screws under the rubber grip.

 

[mdarnton]

A few years ago I had a lens CLA'd by a very popular authorized service house, and it came back focusing past infinity. I called to complain and they put the tech on the line. He said that Nikon had recently advised doing that at a seminar because certain AF cameras like my D300 would not give a green light manual focusing at infinity unless you went past, sometimes. Everyone knows infinity is infinity, but people complained, so that was their response. I do a lot of scale pre-focusing and it was a real irritation. I sent it back, he put it right, and he told me that from then on if I sent a lens in to remind them to keep infinity where it belongs.

All I can tell you is that this is what I was told, that it was a service policy at that time. Perhaps your lens got run through during that period.

 

[macfred]

Same here with my Pre-Ai Nikkor-P Auto 105mm f/2.5. I'm used to the problem - just have to pull it back a little to get right infinity focus.
It's one of my most beloved Nikon lenses ever!

 

[bunip]

When my father brought me in the 80's my first Nikkor 180mm f2,8 ED directly from japan I read in the user manual that there wasn't the infinity stop; i do not remember if for focusing in extreme conditions or for IR photography, but i do know that it's normal.