Rokkor 40mm: Infinity focus problem on Leica m4 m

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Jlafuria

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Hi, I have recently purchased a Minolta Rokkor 40mm first version (similar summicron c 40mm). I mounted this lens on my Leica m4 and I notice a problem to focus at infinity. I already know that the cam is not the same as the original summicron but I got it because was a good deal.

Here below a photo as you can see the problem at infinity.

Is it possible to fix this problem? Where can I work on lens or telemeter?
(I have already some experience to fix cameras).

Thanks to everyone in advance

Jacopo


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Does the rangefinder patch of this camera align correctly at infinitely with other lenses? It is more likely for the rf to go out of calibration. If it is the lens, it would probably be assembled wrong.
 
I have two m4 and in both the lens didn't focus at infinity. The telemeters are both good with other lenses. Wrong assembled in which way?

Thank you
 
Jlafuria said:
I have two m4 and in both the lens didn't focus at infinity. The telemeters are both good with other lenses. Wrong assembled in which way?

Thank you
Click to expand...

When someone takes the lens apart for servicing, there are, I believe, about three ways to reassemble the helicoid, and only one of them is right! A mistake will cause a focus problem! It is correctible, if that is what is wrong with it; but it might cost the price of a CLA.
 
I had latest version of this lens. Ended up buying nos focus assembly.
Helicoid threads where thin and soft. Pushed too hard during CLA and it was it.
 
Jlafuria said:
there is maybe a guide to disassembly that lens correctly?
Click to expand...

As already pointed out here, also I understand that it is a bit difficult lens to disassemble and put back together again – even for pros.

Mine suffers from looseness in the focus ring. I am told that changing factory grease would probably fix it.

The issue here is that CLA is about 150 (dollars/euros), which is quite a lot considering the value of the lens itself. I'm on the fence whether to have it fixed or not – talk about first world problems..

Anyway, here is a dude working on summicron c on Youtube. He appears to know what he is doing.

https://youtu.be/8lSdBFxc-a0
 
Does it really matter? No one takes a photo of something at infinity. And 2.0 DOF wide open is still quite generous.
 
If the problem is really a mis-threaded helicoid, then the focus might be further off at other distances, as there is a chance that with a misthreaded helicoid the slope (rate of ascent) ends up being wrong as well.
 
TenEleven said:
If the problem is really a mis-threaded helicoid, then the focus might be further off at other distances, as there is a chance that with a misthreaded helicoid the slope (rate of ascent) ends up being wrong as well.
Click to expand...


I seriously doubt there is anything wrong with the lens. The CL lenses had a courser focus cam than the M series and Leica relied on DOF for any minor misalignment. They never recommended the 90 Summicron on the CL series. The CL was a consumer oriented camera to compete with cameras like the Rollei 35. Before you do anything with the lens I suggest you put it on the camera on a tripod and focus wide open at various distances with the RF. Then examine the film.


Read https://cameraquest.com/leicacl.htm in particular the section titled CL Weak Points:
 
Thank you all for your help.
I double checked borrowing from a friend his summicron 50 V3.
Same issue at infinity. At this point I think that is the telemeter.
Anyone know how to calibrate at infinity?

Thank you in advance


Jacopo
 
Jlafuria said:
Thank you all for your help.
I double checked borrowing from a friend his summicron 50 V3.
Same issue at infinity. At this point I think that is the telemeter.
Anyone know how to calibrate at infinity?

Thank you in advance


Jacopo
Click to expand...

There are several YouTube videos showing how to adjust the cam. It looks easy enough. Here’s one: https://youtu.be/lE7Yh5BgJ0I
 
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