Nikkor-P 105 f2.5 - need help

[menos]

Hello fellow Nikon RF users, I need a little help with this lens.

In order to collimate my LTM version of this lens, I need to get to the main shim.

I was under the impression, this lens was designed with use of the optical head in Nikon's reflex housing in mind, so the optical call could be easily unscrewed.

Is this correct?
Can the Nikkor-P 105 f2.5 in LTM mount be easily separated or do I have to dive into the lens with more serious disassembly?

Thanks for any help …

 

[Phil_F_NM]

If your front element is well secured to the optical module, you should be able to grab the chrome ring in front of the aperture and simply twist it off. Some of the lenses have grub screws in the focusing barrel which lock the optical module in. If yours does, loosen them up a few turns then unscrew.

If the front optics group separates from the rest of the lens leaving the aperture and rear group in the focusing mount, you're going to have to do some dismantling to get the helicoid apart then to unscrew the rest of optical unit so you can pull it out from the front.

Once you get that whole optical module out, you can adjust the focus by adding or subtracting shim thickness. I've used copper tape to add thickness and correct for backfocus.

Phil Forrest

 

[menos]

Hey Phil, thanks a lot for the heads up!

I was really preparing in my head a quick and simple main shim calibration on the 105/2.5, since I really wanted to try it on the Mono.

I have a most beautiful, absolute mint copy lingering for a long, long time in my dry cabinet.
I bought this at the same time, as my Canon 100/2 LTM Sonnar and simply fell in love with the Canon back then.

Now I had the 105 on the Mono without calibration but simply love it's look a lot! What a lens!

I am a bit spoiled by the ease, many of the Canon lenses are designed, to easily access the main shim between focus mount and optical cell, heck Canon even shimmed rear group on many lenses and designed the access to be easy, so even corrections of focal length are a walk in the park with them.

I dug a bit on the net, and it indeed seems, that the Nikkor-P 105 f2.5 in LTM mount cannot be simply opened but needs further disassembly to correct focussing issues the right way.

 

[Phil_F_NM]

The best way to permanently adjust that lens for a particular body is to find if it is front or backfocusing with respect to the camera. Ensure that hard infinity focus is good then add or subtract material from the front of the intermediate cam follower to give you a proper focus up close. The only distances which would possibly not improve would be the not-quite-infinity range at wide open aperture. Since it's a Sonnar, it does exhibit a very small amount of focus shift but when I was using mine on my M9, I had it in the sweet spot I think and I usually used the lens around f/4-f/5.6 which mitigated focus shift throughout the range.

If you can get it perfectly dialed in, it's one of those lenses that is every bit as good as modern offerings but it lends that Sonnar look to images making them truly stand out. Well worth the work to get it exactly how you want it.

Phil Forrest

 

[menos]

Hey Phil, this is exactly, what I am going for.

Your procedure is exactly, what I usually do, to get a quick verification on a new lens.
I did a quick fix, shimming a LTM-M adapter, to use the lens for some test shots, while on the road, to get a basic idea of what it does.

I have to say, that I get a glimpse of understanding, why so many people around RFF seem to love this lens ;-)

It is almost unbelievable, how good this lens is, considering it's date of creation.