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Losing the 'rangefinder coupling'


reddot925

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Could somebody please be so kind to explain the below case when using non Leica lens on the M9/M10 to me please, and how do you fix it, do we remove the lens and mount it back again or something else?   Thank you!

 

 

"In practice, the rangefinder coupling disengages below 0.9 meters on my sample. According to members of the RFF forum, it is caused by a shorter focus lever than the one built in Leica lenses. Some users did succeed to fix the issue but I have not attempted it since I seldom need to go below 0.9 meters in street photography. This being said, it means that one will have to always remember as he converges towards the minimum focus limit, that he risks to lose the rangefinder coupling."

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Could somebody please be so kind to explain the below case when using non Leica lens on the M9/M10 to me please, and how do you fix it, do we remove the lens and mount it back again or something else?   Thank you!

 

 

"In practice, the rangefinder coupling disengages below 0.9 meters on my sample. According to members of the RFF forum, it is caused by a shorter focus lever than the one built in Leica lenses. Some users did succeed to fix the issue but I have not attempted it since I seldom need to go below 0.9 meters in street photography. This being said, it means that one will have to always remember as he converges towards the minimum focus limit, that he risks to lose the rangefinder coupling."

It only really matters on older film bodies, when I use my 50mm summicron on my button rewind M2 the lens can focus closer than than the body. The rangefinder stops moving at .75m while the lens can actually focus down to .65m.

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When you take the lens off you see the roller can in the top of the lens mount just inside the body. With no lens it is as far out as it goes. This corresponds to the minimum focus distance that the rangefinder will measure (0.7m typically). All the way in corresponds to infinity focus. There is a corresponding part on the lens that moves in to the camera body as you focus to infinity and away from it as you focus closer. Some lenses, especially ZM and CV lenses have the ability to focus closer than the RF cam will move; i.e. The lens moves further away from the body, and the roller cam is in the position it is in when no lens is attached. This is losing rangefinder coupling - the lens is no longer coupled to the RF mechanism in the body. Some lenses not wholly compatible with the Leica M mount will lose coupling before 0.7m.

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Sorry I mean how do you gain the coupling back ? Unmount and remount the lens or simply focus longer and it will couple back?

 

It will couple back automatically when focusing at 0.7m and above. There is no need to unmount the lens nor to focus at infinity at all.

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That's great to hear!  Thanks.

 

Look inside the lens mount, at the top. That's the rangefinder cam you can see - touch it gently and it moves inwards, let go and it springs back out.

 

Look at the back of your lens (unmounted). Turn the focus ring and you'll notice how the rear most ridge moves in and out?

 

When the lens is on the camera, as you focus, that ring moves the rangefinder cam and that's how the focus mechanism works.

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  • 1 year later...

I just got my hand on an M8, seeing little use in recent years, I assume. The sensor looks very clean, so that's good news. However, the roller has a tendency to get stuck at the inner position. I guess there is a need for lubrication and/or a new spring or something. Any suggestions what I can do without sending the body away for a CLA? On another forum, I see that it is suggested to put the body in the sun for some time, to warm the lubrication. I assume this is not the recommended way to solve the problem (something I have not tried, yet...).

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You can work it  back and forth a bit to see whether you can get it to move freely again. Heating seems to me not to be an optimal solution: the first day of winter will get it stuck again. It should not be too expensive to have it seen to by a third party repairer.

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