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Rokkor 58mm f1.2


Active Member
Well I got my M42 adapters from poland the other day and pulled my old Minolta lens apart. There are eight screws through the flange and into a spacer. I pulled the flange off, turned the diameter of the adapter to fit, and machined counter sunk holes in the adapter. I put it together, mounted it on the camera and thanks to Klaus' instructions on setting up old lenses I took a couple of shots in the house.

The shots looked good exposure wise and the autofocus light came on when it should. Now I have to fix infinity focus. The rokkor was set at[focal plane distance?] 43.5mm from what I have read and the sigma is 44mm. The original flange was 1mm thick and the adapter 1.5mm. So I will shave .5mm off the adapter and .5mm off the spacer and I think it will be done.

I will send photos and a write up when it is done..............Tom C


Active Member

Here are the steps taken to convert a Minolta 58mm f1.2 lens to a SD14.

The lens at the start.

th_Rokkor 58mm 001.jpg

Then the flange removed, auto aperture linkage discarded and displayed with the M42 adapter.

th_Rokkor 58mm 010.jpg

Boring bar setup to remove the lip

th_Rokkor 58mm 012.jpg

Then the thickness reduced from 1.5 to 1.0mm to match the original mount

th_Rokkor 58mm 013.jpg

The before and after of the M42 mount

th_Rokkor 58mm 014.jpg

This is the minolta spacer that needed to be .5mm thinner to get infinity focus.

th_Rokkor 58mm 015.jpg



Active Member
Last steps

The end of the lens barrel had to be filed to clear the Sigma dust sheild at infinity focus. There are only a few thousanth's clearance. It just barely fit.

th_Rokkor 58mm 019.jpg

Here the lens is finished with the filed end and machined parts blackened.

th_Rokkor 58mm 023.jpg

Here is the lens on the camera.

th_Rokkor 58mm 002.jpg

th_Rokkor 58mm 004.jpg

A quick shot of a carved bird in a basket ISO 400 f1.2 about 2 feet away. It looks a little soft. I will have to take it out to see what it will do when the weather improves.

th_Rokkor 58mm 021.jpg

........................Tom C

Guest .

Hi Tom,

thanks an awful lot for that busy and highly interesting contribution! :z02_respekt::z02_respekt::z02_respekt:

If I had valuable Minolta lenses ... nothing could hold me from recreating your conversion-procedure. (A lathe is waiting in my garage ... ;))

The example pic is a slightly unsharp?! Open aperture I think?! Does the lens gain more sharpness when slowed down a bit?

See you with nice pictures



Well-Known Member
Well, for f:1.2, it is actually showing pretty good accutance to me! I am amazed at the workmanship you have put out to generate a nice fit of the lens mount! Awesome!