M39 lenses with a "tongue" sticking out the rear

[connloyalist]

Something just occurred to me and I would like to double check if I am correct.

I sometimes see lenses (for example various Steinheil Culminar 135mm lenses) that have a "tongue" that slightly protrudes from the rear of the lens. Is this a (or, the) rangefinder coupling? And if yes does the presence of such a "tongue" indicate that it is in fact an M39 for Leica and not an M39 lens for Braun Paxette? Is the reverse also true (no tongue = Braun)?

Example picture from eBay:



Regards, C.

[connloyalist]

Answering my own question: Probably not, because Leitz lenses do not have this "tongue". So the question the n becomes, what is the purpose of this?

Regards, C.

[kds315*]

Yes, Leitz lenses DO HAVE such, as it transmits the focus information to the camera to adjust the viewfinder.

[DConvert]

[stevemark]

[connloyalist]

So if a lens has a "tongue" then it definitely is a lens designed for a Leica. If it does not have the tongue, it might or might not be. Correct?

Any other way of distinguishing a Leica M39 from a Braun M39 lens by looking at the lens?

Regards, C.

[Lightshow]

The "Tongue" is only on longer focal lengths, 90mm seems to be the transition point, I have a few with and a few without the tongue, shorter lenses seem to use a ring with a helicoid that's driven off the main helicoid/focus ring, and longer lenses seem to all have the tongue, I assume it has to do with the the change in how much the optics have to move for the plane of focus to go from MFD to infinity, longer focal lengths require more movement to cover that range. Beyond 135mm they moved towards Visioflex for a TTL operation.
Edit: Yes, the tongue is an exclusive (to the best of my knowledge) feature of LTM.

[stevemark]

[philslizzy]

I'm 100% certain that its a LTM version. This lens wasn't made for Braun, only LTM and Exakta to my knowledge. It will have the initials VL on the front

LTM lenses that don't rotate internally when they're focused just use this 'tongue'. many lenses have one. It lines up with the rangefinder coupling. The Brauns use a full circle type of coupling. I doubt one like this would work on Braun.

my 135 lenses with tongues; Hektor Canon and Tanar

[yoyomaoz]

If you think about it, it makes sense that only longer focal length lenses should have this "tongue". In these older lenses the helicals and the optical components are at the front of the lens. If the lens is to be rangefinder coupled it is necessary that the position of those lens elements is transmitted to the camera's rangefinder arm. This "tongue" moves in and out as the lens is focused to convey that to the rangefinder. Shorter focal lengths do not require it as there is a rim on the back of the optics which moves the rangefinder arm instead. Just as this "tongue" does.

[philslizzy]