105 2.5 focus issue

dfoo · 11-07-2009

I tested my 105/2.5 nikkor lens. I always suspected the focus was off, but now I know it is. I photographed a long tape, with the focus on the 5 foot mark. The real focus was about 2.5 inches before. I then measured 5 feet from the lens, and set the distance scale at 5 feet. The focus was dead on, but in the rangefinder looked off.

I checked the mount, and I figure its a matter of moving the bar that pushes against the roller arm and cam in the camera. If I can get the distance scale and the rangefinder to match up, then things should be good. This bar appears to be spring mounted in the lens, but I cannot determine any more than that.

Is my plan good? Anyone have any idea how to adjust the bar?

Brian Sweeney · 11-07-2009

What mount is it? I had a Nikkor 13.5cm F3.5 in Leica Mount and a Canon 135/3.5 also in Leica mount do the same thing. In both cases, I built of the RF cam of the lens with copper tape to correct the problem.

dfoo · 11-07-2009

The lens is screw mount. I guess building up the cam is another solution. The cam position itself cannot be adjusted?

digitalintrigue · 11-07-2009

I had a 105 like that but I couldn't find anyone who wanted to tackle the problem, so I sent it back to the dealer...

Brian Sweeney · 11-07-2009

If there is a way to set it, I'd love to know it! I have not figured it out from taking the lenses apart. The copper tape works, and has lasted. Sounds like one strip of copper tape or aluminum foil should do it.

dfoo · 11-07-2009

Sounds strange that there is no way to adjust the mount. Did you try taking the RF cam off the lens mount? It looks to me like the cam is held on with a single screw, and mount is held on with two screws.

dfoo · 11-09-2009

Brian, I took a look at the lens tonight. I first tried a small piece of tape on the RF cam in the lens. That resulted in the opposite of what I wanted, meaning the RF cam needs to be shortened somehow. I ended up putting small pieces of foil under the screw-mount adapter. 6 pieces seems to be the right distance. Tomorrow I'll try some focus test shots, and see how it works now! Hopefully that sorts out the issue.

BTW, to check that it wasn't the screw mount adapter that was messed up I tried a second adapter I have. It had the same issue, so it appears to be something to do with the screw mount of the lens itself.

dfoo · 11-11-2009

I did some test shots this evening and just took a look at them. The lens focuses perfectly now! Looks really great.

Brian Sweeney · 11-12-2009

That is good to hear. Six pieces of foil means the lens was way off, foil is typically ~0.1mm in thickness per layer. It had to be misassembled at some point. I'll dig the parts Nikkor LTM 13.5cm F3.5 out and look it over again.