Is it possible a Leica LTM to M adapter can be off?

[rtai]

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I only use original Leitz Wetzler screw mount to M adapters. The 85mm f1.5 Summarex has a tripod mount and I never questioned why the mount is 15 degrees at an angle when I mount the lens onto M bodies given ltm lenses always a little off center when adapted to M. I never had much luck focusing the Summarex on the M7 and given it’s an 80 year old lens I assume it needs a CLA. But with live view i realise the Summarex is an extremely capable lens and the rf focusing is off. I have another 9cm Leitz adapter and swapped it. To my surprise the tripod mount on the lens is now flush with the bottom plate of the M10. Surely that would affect rf focusing and yes it is now more accurate from wide open minimal focus tests. I have been willing to pay more for original Leitz adapters for the precision but seems my confidence has been shaken. I am now looking for a Voigtlander adapter to test. I can’t imagine a piece of metal like an adapter can get worn out and mine is in good shape. 

[adan]

4 hours ago, rtai said:

To my surprise the tripod mount on the lens is now flush with the bottom plate of the M10. Surely that would affect rf focusing and yes it is now more accurate from wide open minimal focus tests.

Definitely. The 85 Summarex connects to the camera's rangefinder by a narrow central push-rod. Look at the back of the lens with the rear cap off, and you will see the tip of that narrow pushrod sticking out, like so:  \____/

If the lens is mounted 15° off center, it is very unlikely that that central push-rod is connecting to the camera's RF roller correctly (i.e. on the flat central surface). It is either hitting "on the slope" or missing the RF cam altogether.

.....................

Regarding your title question: Of course. Anything made by humans can be "off." Leitz/Leica is very very very good - but they are not "infinitely perfect."

The fact you have a Leitz-labelled adapter that seems to be off indicates that either:

1) one got out of the factory without correct alignment of the external bayonet (M) to the internal thread (LTM). Any factory can produce "Monday morning and Friday afternoon lemons."

2) or it is simply old enough and well-used enough that the LTM threads have been worn enough to allow "overmounting" of a lens - turning it past top dead center by 15°. That will not be very obvious to the eye alone. Some gorilla of a photographer may have been mounting LTM lenses extra tight for years on that adapter, any time since 1954. With each change wearing the threads a little further each time.

However, I have not heard of many such adapters, nor encountered any myself (since I virtually never use them).

[pop]

I don't see how an LTM to M adapter could become so much worn that it mounted the lens at an offset of 15 degrees. Could it possibly be a special adapter meant to be used on a particular lens?

[250swb]

Many LTM lenses are meant to be offset on an LTM camera, so with a viewfinder or flash in the shoe that blocks the normal view of the lens over the top the photographer can look to the side and see the lens settings. But the Summarex has it's lens markings up the barrel and away from the mount and out of the way of being blocked by accessories, so presumably Leica designed it and it's tripod mount to sit centred on the body. So there are two types of LTM to M adapter, one that maintains the LTM offset on an M body, and one the centres the lens, you need the one that centres the lens for the Summarex.

[UliWer]

When I read your posting, I thought: "Well, this is one of those theories...".

Well, trying two different adapters with the Summarex on the M3 taught me better:

1. Tripod mount approx 15° off:

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2. Tripod mount straight:

 

Two adapters, the "straight" one on the right:

Two adapters rearsides:

 

 

 

 

[a.noctilux]

As in the past, I used cheaply made adapter, but now only Leitz or Voightlander M to LTM adapters.

Out of curiosity, I had some surprises when I took some random measurement on these adapters.

Since some years now, I know they are not of the same thickness, before mounting M-LTM adapter marking Leitz, I measured the thickness with digital calipper.

 

Some have that famous 1.00 mm thickness around the mount 👍.

Some have 0.98 to 1.02 mm depending where around the mount, strange as when made this must be 1.00mm. Deformations ?

Some have consistent 0.97 to 0.98mm (these may be worn out with use, and times of thousands on/off).

Brass could be choosen for that property.

 

 

[rtai]

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I kept a few 28/90 adapters for 28mm lenses so never noticed any inconsistencies.  Learn something new everyday. Anyway the Summarex is a terrific lens. 

[a.noctilux]

If you have digital caliper at hand, it would be interesting to measure their thickness,

at different places.

As side note, I've discarded a couple of Leitz LTM-M adapters, too much worn out or with 'invisible bending' ( incredible ) when placing on flat surface.

[250swb]

4 hours ago, a.noctilux said:

If you have digital caliper at hand, it would be interesting to measure their thickness,

at different places.

As side note, I've discarded a couple of Leitz LTM-M adapters, too much worn out or with 'invisible bending' ( incredible ) when placing on flat surface.

Why assume it's the adapter thickness, why not also consider how the threads are cut?

Edited September 11, 2021 by 250swb

[a.noctilux]

46 minutes ago, 250swb said:

Why assume it's the adapter thickness, why not also consider how the threads are cut?

That is another possibility.

The beginning ( or ending ) angle of thread cut.

 

As this can be funny to investigate, I took time to simulate with my dozen of adapters.

Screwing a lens then note the stop angle with each adapter.

This angle comparing to red dot and top cutout (assuming those stay always at same place) is different with each adapter 🤥

[M9reno]

Damn - I can feel this thread firing up all my neuroses.🙂

[a.noctilux]

Just to be positive,

@rtai can you say which of the adapter with or without angle 15° works better for RF focus ?

I don't have Summarex, just out of curiosity.

[rtai]

2 hours ago, a.noctilux said:

Just to be positive,

@rtai can you say which of the adapter with or without angle 15° works better for RF focus ?

I don't have Summarex, just out of curiosity.

The one that’s not off by 15 degrees is more accurate but still not perfectly accurate. There’s shop with a dozen Leitz 28/90 adapters and I will go there tomorrow and test everyone. 

[Alberti]

When I sent my Canon 1.4 lens to Will van Maanen, I sent along the adapter too. The focus alignment of the combo is great. [But like always with these adapters, the lens is off-centre. It is a Cantonese adapter.]

Edited September 15, 2021 by Alberti

[a.noctilux]

On 9/12/2021 at 2:06 PM, rtai said:

The one that’s not off by 15 degrees is more accurate but still not perfectly accurate. There’s shop with a dozen Leitz 28/90 adapters and I will go there tomorrow and test everyone. 

Did you test the adapters of the shop ?

Just curious if they are fine or not.

[rtai]

On 9/16/2021 at 4:39 AM, a.noctilux said:

Did you test the adapters of the shop ?

Just curious if they are fine or not.

I went to the shop but the salesman I knew wasn’t there and I didn’t want to ask the other guy if I could play with the adapters. Anyway I ended up buying an SL2 due to ease of focusing longer M lenses. It’s very difficult for me to focus the Summarex with the rangefinder and any conclusion unless very obvious like my defective M/LTM adapter being 15 degrees off would be suspect given my eyesight. The SL2’s high resolution EVF with the magnification and peaking are perfect for M lenses and except for the size is really what I need. If Leica made a Monochrom SL I would be all over it.

[a.noctilux]

Nice 👍.

SL2, wow.

Another solution to an old problem 👌.

 

How about weight/size ?