Need help with 20mm MIR-20N with Nikon Mount

[M. Valdemar]

I bought a MIR-20N on eBay and just got delivery from Russia. The glass is in beautiful condition, but I have a couple of problems with it.

I wonder if anyone knows about this lens. I don't want to open the lens mount before I know what I'm doing.

1) The lens doesn't quite focus to infinity. It's a little bit off. The lens needs to be a tiny bit closer to the "film plane". I was thinking if I removed the Nikon mount, would there be a shim I could remove? Infinity focus is just a little off, but it is creating unsharpness on what seems to be a good len.

2) The coupling ridge on the lens is too low. It doesn't engage the AI tab on either my Nikon D700 or Nikon F100. It just barely makes contact on an old Nikon N70. I was thinking of gluing on a piece of plastic just to hit the tab, maybe using crazy glue? It can't be bent.

Does anyone have any experience adjusting this lens?




(the AI coupling is just a cut-out, but I think this is the way it came from the factory)


(here you can see the AI tab not hitting the coupling ridge)

[madamasu]

Hi Valdemar,

I also got a D700 and the Mir-20N, and things look exactly the same, but I don't really see this as a big problem, as I guess you will not change the aperture so often. Most of the time it will be between 5.6 and 8. So I just give the information needed to the camera via the lense-information function in the menu and take pictures.

best
Thomas

[M. Valdemar]

How about your infinity focus? Is it correct?

[madamasu]

As far as I can see, yes.