Leica CL, Rokkor, Hexar lenses and M bodies?

[steve_hotchkiss]

I have gotten confused and could used some sorting out. I recall

reading that some of the non-conventional M lenses when used on a M

body may have some slight incompatibilities like focusing plane

distances. I am wondering about things like the 40mm CL lens and

whether it has problems with an M body or is that just Hexar lenses?

Are Leica M lenses a problem on the CL or CLE bodies? I wonder if

someone can provide a good overview of what works perfectly with what

and what might have problems and why.

[al_kaplan1]

The CL lenses (but not CLE lenses) have the cam cut directly into the back of the focussing helix. In theory if the lens doesn't line up perfectly with the camera's cam follower roller it will not accurately focus on an M camera. In practice I've tried several CL lenses on my m bodies and they work perfectly. Some M lenses won't fit the CL and some older wide angles might hit the meter arm, but they couple just fine to the rangefinder. Never collapse a collapsible lens on a CL!

 

Some M mount lenses, although internally cammed, still have a slight cam angle machined into the rear of the cam helix to "fine tune" it for a lens a hair longer or shorter in focal length. This is very common on 50mm Summicrons. They too work just fine on M bodies. I just wish the 40 actuated the 35 frameline on my M bodies!

[Troll]

The collapsable SummiCRON collapses just fine on a CL.

[johann_fuller]

Al - just file a bit of metal off the mount that actuates the frame selector - I did this on my 40 Rokkor to use on my M6 - enables much more accurate framing at long and medium distances. Ok it's irreversible if you want to sell it later but I want a tool not an investment. I have never properly understood the CL - M incompatibility - the RF cam on M lenses has to move a certain ( about 2.63mm ) distance to measure infinity to 1m. It has to move this on all focal lengths and it's only the lens group that is on a secondary cam (on anything other than a 50) that moves at a different rate. I would like a proper explanation as I haven't examined a CL lens.

[al_kaplan1]

Johann, if you look at the back of a a 50mm lens (my 35 Summicron also) you'll see a brass tube just inside the chrome mount that turns and moves in and out as you focus. with the 50's the optics and brass tube move the same amount in and out while focussing. With a sorter focal length lens the optics move less than the tube, which rides on the camera's rangefinder follower (that roller at the top of the lensmount). The helical threads that move the optics are set for the "average lens" of that focal length. Leitz at one time made many slightly different focussing mounts for the same lens. They'd choose one to match a particular lens. At some point (late 60's?) they decided to just machine a very slight cam into the back of the brass tube for fine tuning, a much more cost effective way of matching optics to the rangefinder. All lenses of a particular model could then use the same basic focussing mount.

 

As a cost cutting measure they decided to make the CL lenses with no internal camming. Instead a relatively steep cam is ground into this brass sleeve. This requires much more accurate positioning of the lens in the camera than using the prior system. In practice, if the M cameras weren't built to that level of accuracy something was wrong! Every CL lens I've tried worked just fine on my M bodies, and those M lenses which will fit without hitting the meter arm work fine on the CL.

[johann_fuller]

Cheers Al - now I can visualise the CL system. My 50mm Summicron (3rd version) has the machined cam and an individual cam rate as it's stamped on the focusing barrel - I reckon this is super fine adjustment as some lens groups will fall between the different cam rate mounts that they made. Something not found on CV or Hexanon lenses and I guess another reason why you pay the extra for the Leica lens.

[victor_mecyssne]

You asked about the 40mm, a lens with which I have no experience. However,

I have used a 28mm Rokkor (w/ accessory viewfinder) on an M3 and the

compatability was flawless. The lens was an excellent performer. Hope this

helps.