Leica 40mm Summicron-C focus cam adjustment?

[happy]

Hi all,

I received a 40mm Summicron-C which is in good shape except for the fact that the lens cam is off. Has anyone had any experience fixing this issue? What should I expect to pay if I send it to Leica? I got a good deal on the lens so if it's reasonable I could imagine sending it in with my M8 since it has a dead pixel that needs to be mapped.

I've asked a local repairman and he wasn't comfortable doing this repair. Said it might run a few hundred, which may not be worth it for me since I could get a clean copy for less with a return.

Thanks

 

[Monochrom]

hi, isn´t your M8 off? did you test it´s alignment?

Once i saw an M8 that had a different adjustment of the arm that houses the RF wheel. It gave me different focus point than my m9 with the same lens.

Check on that i think there might be something.

 

[happy]

hi, isn´t your M8 off? did you test it´s alignment?

Once i saw an M8 that had a different adjustment of the arm that houses the RF wheel. It gave me different focus point than my m9 with the same lens.

Check on that i think there might be something.

I considered this but other lenses line up perfectly at infinity so I think the problem is with the lens. I will try the lens on another body tomorrow and see if that somehow fixes it.

 

[Phil_F_NM]

The focus cam itself can't really be adjusted, only the double helicoid can be "adjusted." By "adjusted" I mean a part of the helicoid can be moved over one thread this way or that. These lenses were designed with no real adjustment capability with regard to the helicoid. Have you tested it for true infinity focus optically? That is the real test. If it makes a good image at infinity and a few closer distances, then your RF cam is probably out of adjustment.

Phil Forrest

 

[happy]

The focus cam itself can't really be adjusted, only the double helicoid can be "adjusted." By "adjusted" I mean a part of the helicoid can be moved over one thread this way or that. These lenses were designed with no real adjustment capability with regard to the helicoid. Have you tested it for true infinity focus optically? That is the real test. If it makes a good image at infinity and a few closer distances, then your RF cam is probably out of adjustment.

Phil Forrest

Hi Phil,

I definitely have gotten the impression that the cam itself isn't really adjustable. Hewn from a single piece of brass and locked into the mechanics without any means for fine tuning.



At infinity hard stop, it seems that the lens does have sharp focus on far away objects. But the cam is only a tiny bit off... the DOF might cover it at that range even if it is off.

I carefully disassembled some parts and saw the helicoid... should I try and move it over one thread? Would that adjustment be very fine? Because it's only off a tiny bit. Maybe a few degrees.

I was toying with the idea of cutting a shim to go between the lens moutn and lens, and machining off an equal amount from the spacer inside the lens. This way, distance between lens elements and sensor would stay the same but the RF cam would be further away, hopefully fixing the issue. In my head it might work... But it seems like the tolerances are seriously tiny so I'd like to avoid trying this even though I have some machining skills.

 

[k__43]

I had this problem where my M2 couln't focus the cron-c at all - other lenses seemed good enough. My 90/2.8 was front focusing a bit but I could lean into it.
After I adjusted the camera to be working with the cron-c all other lenses where perfect too

the cron-c is very sensible to where the arm roller touches the cam, when this is off other lenses might be okish with it but the 40mm not

 

[happy]

I had this problem where my M2 couln't focus the cron-c at all - other lenses seemed good enough. My 90/2.8 was front focusing a bit but I could lean into it.
After I adjusted the camera to be working with the cron-c all other lenses where perfect too

the cron-c is very sensible to where the arm roller touches the cam, when this is off other lenses might be okish with it but the 40mm not

oh really? 🙂

I will have to give this a shot then! Much simpler fix!

Who adjusted your rangefinder? Leica? How much did it cost you?

 

[happy]

So I've found that the lens works perfectly if it's mounted, but held in place ~2 degrees before it clicks solidly into place. This 'calibrates' the cam with my M8. I've tested with a focus tester and this perfectly corrects the front focus and infinity alignment.

My new plan now is to find a donor Leica lens mount, machine new holes to be lined up with the Summicron-40 with 2 degree rotational adjustment. That way I do not have to modify any of the original parts in any way and can restore it if I wish. I can also do the modification to bring up 35mm lines without messing with original parts!

I think I may cannibalize a OTZFO (the mount thickness seems to be the same) but if any of you have a suggestion for where to find cheap donor parts, I would appreciate it!

 

[k__43]

So I've found that the lens works perfectly if it's mounted, but held in place ~2 degrees before it clicks solidly into place. ...

this sounds exactly like i thought .. your RF arm is set too long and this doesn't hurt with straight cams but it does with the cron-c since it has a angled back to translate to a pseudo 50mm movement. (sorry I am non-native english so I can't explain this better - maybe someone like Dante Stella can explain RF coupling and the speciality of the Cron-C 40mm better)

You need to adjust the M8 RF to your lens, your other lenses should still be still fine afterwards - no need to change parts on the lens. adjust the rf arm length and then the infinity setting. it sounds more difficult then it is really

K