Collimating Nikkor P.C 85/2 - DIY-able ?

[hans voralberg]

I just bought a Nikkor 85/2 LTM from ffordes, it's gorgeous except for some oil on the blades and that it front-focus, by about ~1-2cm. It doesnt look like it has been tinkered with or anything like that. So is there a not-too-hard way to collimate it myself or I have to send it to a technician. Most of my kit are being CLA by CRR, so I might as well send it there, but I need something to shoot with now, so if there's a way I'd like to try.

 

[Sonnar Brian]

If it is focussing in front of what is indicated by the RF, the Shim needs to be reduced slightly. Like 0.1mm or so. The optics should "just unscrew" from the lens mount, revealing the shim. Another RFF member did this on his lens, but i have never done this to my 8.5/2.

Make sure that the RF of the M3 is not slightly off- the 8.5cm f2 is about the same DOF as a 50/1.4.

This is a good lens

 

[VinceC]

The 85/2 has the most critical depth of field of any standard (not superfast) Nikon RF lens. At minimum focus of 42 inches, the depth of field is just .68 inch. By comparison, a 50/1.4 focused at 36 inches has a 1-inch depth of field.

Even a 50mm f/1 or f/1.1 lens has more depth of field -- about .75-inch at 36 inches.

So the 85/2 is bound to show focusing errors in the camera RF that aren't apparent with any other lens.

 

[Harry Lime]

I would send it in, unless you have an optical bench to adjust it.

Very nice lens by the way.

 

[hans voralberg]

If it is focussing in front of what is indicated by the RF, the Shim needs to be reduced slightly. Like 0.1mm or so. The optics should "just unscrew" from the lens mount, revealing the shim. Another RFF member did this on his lens, but i have never done this to my 8.5/2.

Make sure that the RF of the M3 is not slightly off- the 8.5cm f2 is about the same DOF as a 50/1.4.

This is a good lens

Yes it is focus on whatever is in front of the indicated point

So supposedly I'd need to remove/exchange the shim ? I'm testing it on my R-D1, I know it's not the best to test but that's the only body I got atm.

 

[VinceC]

Hans,
The RD-1 does not have the focusing accuracy to consistently focus an 85/2 lens. That's why Cosina only makes an 85/90 F3.5.

 

[hans voralberg]

Yeah I just figure that out, 25% of my test shots are in focus =) I guess I need to wait for the M3 to get back, is the R2M any more accurate ? Anyhow, I open up the lens as far as I can figure out how to, and seems like there's a screw to adjust the focusing cam, pics below, am I right about that ?

 

[splitimageview]

Here is an interesting thread about focusing accuracy, with charts for various cameras. http://www.rangefinderforum.com/forums/showthread.php?t=55500

 

[ferider]

I have had 6 different LTM 85/2 Nikkor's, most of them now being used by other RFF members. For all of them the focus was accurate, measured with M3 AND magnifier. The Nikon QA back then for this lens was very, very good.

Chances are high that it is either the camera, or you are not testing correctly (use the dead center of the patch, a cable release, tripod and magnifier, otherwise backlash can very easily lead to such a small error.

I myself have tried to focus the 85/2 on a friend's RD1 and failed. EBL was too short for my coffee and nicotine polluted body 🙂

I recommend to exclude all other possible sources of error first, before re-shimming the lens.

Roland.

 

[venchka]

Been there...

Been there...

I have had 6 different LTM 85/2 Nikkor's, most of them now being used by other RFF members.
...

I myself have tried to focus the 85/2 on a friend's RD1 and failed. EBL was too short for my coffee and nicotine polluted body 🙂

Roland.

...done that. A proud member of both groups! 😱😀😎

Now, if Roland would just offer me a 10.5cm/2.5 LTM lens. 😎

 

[hans voralberg]

Seems like I'm wrong and should buy a magnifier =) shame I have no paypal lol. Thanks guys, the accuracy chart was most helpful