LTM puzzler

This is a followup to my recent post asking about 28mm LTM lenses.

Today I received a very nice 28mm f/3.5 Avenon lens, which came with a 35/135 M-mount adapter that was easily removed. For my first test I mounted the lens on my Canon 7 body and all seemed well as it screwed in smoothly and the marked focus distances seemed appropriate just aiming at things around the house. Then I then tried to mount it on my Canon L2 body but it wouldn't screw in all the way - it smoothly engaged one full turn of the threads (with the focus set at minimum) but wouldn't go any further, it's somehow blocked. It wouldn't even engage the mounting threads when set at infinity. Huh?

The few other LTM lenses I have fit that L2 body with no issues. The back of the Avenon has no unusual or oversized projections (unlike, say, the bulbous rear element of a Jupiter-12) that would interfere, and the threads appear undamaged both visually and based on the fact that it mounts just fine on my 7 and to the M adapter.

It looks like the Avenon's focus knob might hit the L2's slow-speed dial if I could screw it in more, but that's not the issue right now and there's plenty of clearance.

Has anyone ever run in to something like this before?

Steve, is it possible that the thread on the Avenon is not 26 TPI as per original Leica thread mount lenses? Some FED cameras used M39×1. The latter may fit on your 7 but bind on the L2.

Extra note: many of the off brand plastic back caps sold now are M39×1, but they fit, considering the play in the plastic threads.

That's an interesting idea. The Avenon was manufactured in the early 1990s, long after this problem was known, and by successors to Komura, who also made LTM lenses. Given this timing and history one would think they'd know enough to avoid this mistake.

I've got some travel coming up in a few days so will put this aside until I return.

A bit more info...

In addition to fitting my Canon 7, the Avenon 3.5/28 fits and works on a Canon P body just fine, and there's also no trouble screwing on the Chinese-made deep metal rear cap I use for my Jupiter-12. But it absolutely won't mount on my Canon L2. So I don't think it's a thread problem but I'm stumped as to what the issue may be.

BTW, the lens requires a deeper-than normal rear cap. The Jupiter-12 cap is overkill, but the apparently standard-depth caps like I use on my 50mm lenses won't fit.

I'll leave it there for now.

Post a picture of the rear of the lens, and the front of the camera. It's not a very common lens, I think, so most of us won't have had experience with it or even know what it looks like.

From your description of "It wouldn't even engage the mounting threads when set at infinity," I suspect that it doesn't have to do with the threads, but that some mechanical part of the lens such as the rear barrel or RF cam is touching the parts inside of the L2's lens mount (light baffles or whatever).

This blogger (took a while to load; he likes big pictures):


says:

​

Rangefinder Compatability

The Avenon 28mm LTM lens will fit almost any LTM / M39 camera and function properly. Known incompatibility exists with some of the Canon rangefinders.

Do not mount this lens on the Canon V, Canon VI, Canon P, or Canon 7 - it will damage the camera baffles - according to Kobalux.

Dustin McAmera said:

This blogger (took a while to load; he likes big pictures):

Leica MDa | Stockholm | Kodak Ultramax 400 | Avenon 28mm f3.5 LTM — cameraville

The Avenon 28mm f3.5 LTM lens come from a Japanese manufacturer called YK optical in Yokohama, which had a short history of only producing two lenses mainly under the name of KOBALUX, a 28mm f3.5 as well as the 21mm f2.8 LTM…

cameraville.co

says:

​

Rangefinder Compatability

The Avenon 28mm LTM lens will fit almost any LTM / M39 camera and function properly. Known incompatibility exists with some of the Canon rangefinders.

Do not mount this lens on the Canon V, Canon VI, Canon P, or Canon 7 - it will damage the camera baffles - according to Kobalux.

Click to expand...

Thank you, I guess this sort of resolves the puzzle. I'd quickly looked at this page before I bought the lens but missed this detail. Funny thing is, it fits a P and my 7 just fine, it's the L2 where it has a problem. But the fact of incompatibilities with Canon rangefinders is what's important. I'm surprised that a Japanese company (YK Optical) would make a lens that didn't fit Japanese (Canon) cameras, but that's life.

Perhaps I'll keep it, perhaps I'll sell it on in favor of a Canon 28mm. It would certainly be convenient to be able to use all my LTM lenses (not that I have that many of them!) on either the 7 or L2.

If you try mounting it with th film door open, perhaps you can see where it contacts the baffles. If it's just a small interference, you might be able to unscrew the baffle and re-attach very slightly shifted as the screw holes may permit a little wiggle room, or gently bend it. I've bent my Canon 7 baffles to fit the J-12.

I vote for a different lens, Canon.

grain elevator said:

If you try mounting it with th film door open, perhaps you can see where it contacts the baffles. If it's just a small interference, you might be able to unscrew the baffle and re-attach very slightly shifted as the screw holes may permit a little wiggle room, or gently bend it. I've bent my Canon 7 baffles to fit the J-12.

Click to expand...

I should have thought of that!

It’s hitting the baffle at the top of the film chamber, just under the follower. There are two screws that seem to hold the bottom baffle in place, but nothing immediately obvious to adjust the top baffle other than bending it. I’m not inclined to attempt disassembly or otherwise mess with it, so I’ll sell this lens in favor of a Canon lens.

Thanks to all who responded.

Steve Goldstein said:

Thank you, I guess this sort of resolves the puzzle. I'd quickly looked at this page before I bought the lens but missed this detail. Funny thing is, it fits a P and my 7 just fine, it's the L2 where it has a problem. But the fact of incompatibilities with Canon rangefinders is what's important. I'm surprised that a Japanese company (YK Optical) would make a lens that didn't fit Japanese (Canon) cameras, but that's life.

Perhaps I'll keep it, perhaps I'll sell it on in favor of a Canon 28mm. It would certainly be convenient to be able to use all my LTM lenses (not that I have that many of them!) on either the 7 or L2.

Click to expand...

Hi Steve, does the Avenon/Kobalux 28mm f3.5 indeed work on a Canon P body without damaging the internals/light baffles? I’ve purchased one recently off eBay, unfortunately without prior research so I’m debating on cancelling it, however it’s a great deal. I would greatly appreciate your insight and help!

My Avenon fits fine on my Canon P and Canon 7, but not on my L2. My Jupiter-12 fits my L2 and 7, but not my P. It would make my life easier to sell both lenses and replace them with Canon glass.