Rokkor 58mm f1.2

calfee20

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
 

OyvindS

Well-Known Member
Input

Hi Tom

There is a user over at dpreview who has done a conversion like this. You might like to read what he did. Links here:
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Look forward to hear what you think about the result, and to see the pictures.

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
 

calfee20

Active Member
Finished

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

Then
 

calfee20

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 .

Banned
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

Klaus
 

laurence2

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!
 
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