After waiting patently for Cosina (Voigtlander) to bring out some of their lenses in a true "M" mount, I am now feeling that I am wasting time, so I will be buying the screw mount adapter to mount the LTM lens to my M6. For those that have gone this route, I have some basic questions about this process.

1. Do you mount the adapter to the lens, and then the whole assembly to the camera, or do you mount the adapter in the lens mount of the camera and then screw the lens in?

2. When screwed together, does the lens align properly, (focus and aperture mark straight up), on the actual camera? I would imagine that this would entail a very tight tolerance in the thread count, and knowing exactly where the lens would "enter" the adapter's internal threads. Is the machining that precise, or can I expect turning my camera on its side to read the scales?

3. Is there a chance that the adapter could become stuck within the camera, due to the dissimilar resistance of the threads and the M mount release?

Thanks for any words of experience from you LTM lens users. If I didn't think of every possible negative effect of going the adapter route, please fill me in on any other possible problems. Somehow, this seems like quite a compromise after using bayonet mounts all these years.

-- Al Smith (smith58@msn.com), April 16, 2001

Answers

Al:

I have a Heliar 15 with the Cosina LTM to M adapter that I use on my M6. This lens has no focussing cam, so I cannot speak to that issue. The mount threads onto the lens (tightly), lines up perfectly, then the whole assembly mounts and unmounts from the camera like any other M lens. There are three versions of the mount so as to bring up the proper frameline. My setup seems to work great.

-- Jack Flesher (jbflesher@msn.com), April 16, 2001.

The only screwmount lens I currently own is the 15mm. I use it with a gen-u-ine Leica M adaptor and it lines up perfectly. The M adaptor I got with my Komura 2x didn't line up very well (not shocking considering the overall quality of the rest of the package)so the "generic" adaptors could range in quality. I have to believe that Cosina has paid attention to thread timing, it would be a silly omission in an otherwise nicely executed product line. I attached the adaptor to the lens, mounted it on an OUFRO (a M-bayonet extension tube used with the Visoflex) and honked it down wearing rubber kitchen gloves so it's pretty much an M-mount lens until I do the same in reverse. I thought about using a little Loc-Tite but I was afraid for resale value.

-- Jay (infinitydt@aol.com), April 16, 2001.

PS: to clarify, I don't use the lens on the OUFRO, just used it as a wrench to tighten the adaptor. The camera's lensmount is probably tough enough to take it also, but I had the tube so I used it.

-- Jay (infinitydt@aol.com), April 16, 2001.

I've owned a number of LTM lenses, from different manufacturers, and few M-mount ones ($$$$), and have never had a problem. If you're the type to whom appearance (visual centering of the numbers) is important, you might drive yourself crazy with some adapters and some lenses (different lens manufacturers have different ideas about where the "right" place for the numbers is, and off-brand adapters are sometimes unreliable in locating the lens), but they'll always work properly on your M camera, if that's what you need..

-- Michael Darnton (mdarnton@hotmail.com), April 16, 2001.

Al,

To answer your questions:

1. I usually mount the adapter to the lens first, but it works just fine to unscrew a lens from the camera-mounted adapter, and then screw in a new lens. Make sure you have the right adapter for the right viewfinder lines.

2. They're mostly correct. I have one lens that's off by a few degrees. It focuses fine, and it's not hard to read the numbers. Yes, it's pretty tight machining - but how do you think the original LTM lenses worked?

3. No way. The only way to get the adapter to remain in the camera is to unscrew the lens without pressing the lens release button.

If these things were really problems, you'd hear more about them, and Cosina would sell alot fewer LTM lenses. As it is, they work fine in all respects. My only complaint is that it's impossible to put LTM back-caps on the lenses while the adapter is attached (but of course, M back-caps work fine). The adapters are also kinda "sharp," and if you're not used to opening twist-off beer bottles with your bare hands, it's going to hurt a little removing them.

-C.

-- Colin James (colin@longitude.com), April 16, 2001.

1)Yes 2)Yes 3)No

I use a 35mm Ultron and a 50mm Nokton both with the Cosina adapters. The adapters are mounted on the lens and the assembly then functions as one unit. The alignment is proper, the tolerances are tight. If the adapter were to get stuck while removing the lens, the rear Cosina's rear lens cover functions as a wrench to unscrew the adapter.

All in all, I used the Ultron and Nokton very successfully until I had enough sheckels to acquire a used 35mm Summicron. I never had any problems. Lenses coupled very nicely and I was never aware of any difference with a true M mount.

Go for it.

J-D

-- Jean-David Borges (jdborges@home.com), April 16, 2001.

It is hard to imagine aligning the screw threads with perfect consistency, isn't it? But as Colin pointed out, that's exactly what Leitz did, on about 700,000 or so cameras, up to and including the IIIG. As for the adapters, I used to use one with a thread-mount lens on my M2. Not a problem. What I did worry about was whether they could consistently maintain the lens flange to film plane distance--something Leitz was fanatical about--what with two extra machined surfaces to worry about. But evidently this is not a problem either. Not for them.

I say that they were fanatical about the lens to film plane distance because I read that the reason the film tracks are frosted-looking rather than shiny like some other cameras, is that Leica grinds the tracks without polishing. And this is because they found grinding to be a precision operation, and polishing not to be.

When you release the catch and twist to remove the lens and adaptor, the ring stays with the lens. Not a problem.

-- Bob Fleischman (RFXMAIL@prodigy.net), April 16, 2001.

Actually I believe the only disadvantage of using an adapter mounted LTM lens, over mounting a bayonet lens, is that the thread mount affords a smaller throat opening, which can cost some peripheral rays with some lenses. I suppose this is mainly an issue with fast, long lenses.

-- Bob Fleischman (RFXMAIL@prodigy.net), April 16, 2001.

Ah--missed a bit--if you're only using your lenses on an M camera, screw the adapters on and leave them there. They'll stick fine, just like they grew there, and if you want to remove them for some reason, loosen the lens from the M bayonet, but don't pull it out of the front of the camera--then unscrew the lens and pull the loose adapter out of the camera front.

-- Michael Darnton (mdarnton@hotmail.com), April 16, 2001.

1. The former. 2. I have a 75mm Cosina LTM. The focusing marks align perfectly. The machining is very precise. 3. No, unless you forget to press the lens release. If that happens, screw in the lens again, and press the lens release to release.

And if the adapter is 'stuck' to the lens, and you need to unscrew it, the best procedure is to put the M rear lens cap on the adapter and tighten, then unscrew the adapter holding the rear lens cap. Perfectly obvious when you do it, harder to describe in writing. Better procedure than shredding your fingers :-)

-- Mani Sitaraman (bindumani@pacific.net.sg), April 17, 2001.

Thank you everyone. I was hoping for an overall good review of these adapters, and it seems that they operate as advertised. I get some photo journals from Japan, (use to live there), and the new Voigtlander 21mm f/4.0 looks great as far as price to performance is concerned. As little as I would use it, the low price would not be hard to swallow, compared to a real Lieca model.

-- Al Smith (smith58@msn.com), April 17, 2001.