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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
 
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:
http://www.foto.nordjylland.biz/SD14/sd14-nonsigmalenses.htm#Minolta

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
 
Finished

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

The lens at the start.

View attachment 1064

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

View attachment 1065

Boring bar setup to remove the lip

View attachment 1066

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

View attachment 1067

The before and after of the M42 mount

View attachment 1068

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

View attachment 1069

Then
 

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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.

View attachment 1070

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

View attachment 1072

Here is the lens on the camera.

View attachment 1073

View attachment 1074

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.

View attachment 1071

........................Tom C
 

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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
 
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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