M4 RF Adjustment

[Kim Coxon]

The horizontal RF adjustment on my M4 is very slightly out. Searched the Forum and got the links to the various notes which tell me it is adjusted by the RF cam flat screw. However, does anyone have any tips as to how to do it in practice? With all the other cameras I have done, I have been able to mount the camera and lens on a tripod, point it at a TV mast about 20 miles away and adjust the setting whilst looking through the finder. Easy 😉 However, on the Leica M's I can't see a way to adust it with a lens in place. Does this mean you have to make an adjustment, put the lens on, see if it works, take the lens off, adjust again etc etc etc until right or am I missing and easier solution? 😕

Kim

 

[Ken Ford]

If I'm understanding you correctly, you're trying to correct horizontal misalignment, like this: _-_ , correct?

That adjustment is behind the screw on the front of the top plate. The adjustments inside the throat of the mount are for infinity and close focus.

If you're trying to adjust infinity, no lens is needed AFAIK (at least I've never used one, and haven't had problems). Just tweak the roller screw until things are correct with that antenna - it's an eccentric.

 

[Kim Coxon]

Hi Ken,
It is the infinity which is out. The vertical is fine. If there is no lens on the camera, the roller is at the close focus point. If I move the roller back, it is against the backstop, also not at infinity. The basic question is how do I know where the infinity position is without a lens set to infinity on the camera?

Kim

If I'm understanding you correctly, you're trying to correct horizontal misalignment, like this: _-_ , correct?

That adjustment is behind the screw on the front of the top plate. The adjustments inside the throat of the mount are for infinity and close focus.

If you're trying to adjust infinity, no lens is needed AFAIK (at least I've never used one, and haven't had problems). Just tweak the roller screw until things are correct with that antenna - it's an eccentric.

 

[Ronald M]

Qualified repair people remove the plugs in the bottom of the camera. There might even be a special fixture to simulate a lens a infinity so you can see where to put the screwdriver. Also I would design a baseplate with the proper holes if I were a repair person.

I just use the off on trick myself and angle the screwdriver blade.

 

[Branestawm]

Kim, I have a copy of the repair manual for the M2(which you are welcome to borrow) which shows the procedure for setting the rf. This involves the use of a special tool; effectively a ring which fits on the lens mount and has a series of steps which act against the cam follower and give the settings for a series of focus distances whilst still allowing access to the setting screw. Without this gauge I'm afraid your stuck with trial and error 🙁 . And of course as you alter the eccentric you alter the effective length of the arm. To set this there is an eccentric at the pivot end of the arm. Altering this will probably throw infinity out again. More trial and error :bang: . Shouldn't take more than a week or two...

Good luck,

Paul

 

[awilder]

Kim, infinity adjustment by turning the screw under the cam roller is a trial an error technique by checking RF alignment with your lens after each attempt at turning the screw in a particular direction. Minor adjustment to change RF position doesn't take much turning. It's not difficult to do, but the main thing is to know if the lens you're using is accurately callibrated for infinity. Your best reference is a Leica 50mm lens since these are the basis for the rangefinder design on all Leicas.

 

[Kim Coxon]

The intention was to do it with my 50 Cron 😉 This works perfectly with the M2 and M3. If all else fails, it looks like another call to CRR.

Kim

Kim, infinity adjustment by turning the screw under the cam roller is a trial an error technique by checking RF alignment with your lens after each attempt at turning the screw in a particular direction. Minor adjustment to change RF position doesn't take much turning. It's not difficult to do, but the main thing is to know if the lens you're using is accurately callibrated for infinity. Your best reference is a Leica 50mm lens since these are the basis for the rangefinder design on all Leicas.

 

[Stu W]

Kim, this manual has the exact technique. I would set the camera on bulb, and go through the bottom plate with a lens attached. There is a 1/4 turn plug that gives you access to the screws. Stu.
http://mysite.verizon.net/stuems/leicabasicrepair.pdf

 

[Kim Coxon]

Got it Stu, many thanks, that was just what I was looking for. I had a copy of those repair notes (in fact I has reduced them to just over 500Kb rather than 6 Mb, to put on the website) When I read them I saw the comment "the distance adjustment is accessible through the lens opening" which led to the question. I didn't see the bit about the plug on the bottom.

Many thanks again. Isn't this place wonderful!!!!!!!!!!!!!

Kim

Kim, this manual has the exact technique. I would set the camera on bulb, and go through the bottom plate with a lens attached. There is a 1/4 turn plug that gives you access to the screws. Stu.
http://mysite.verizon.net/stuems/leicabasicrepair.pdf

 

[Stu W]

Glad to help.

 

[Ken Ford]

Hmmm. It's been awhile, but I could have sworn I tested and adjusted the infinity on my old M4-P by holding the arm in lightly against the stop. I haven't had to adjust my M6.

Could I have just been lucky before in that the stop was in the perfect position for infinity?