LTM (LeicaThread Mount) to M-mount Adapter Adventure III

This post is to help me keep track of what I’ve learned about adapting LTM lenses to modern digital Leica cameras.

While a LTM to M adapter may mechanically assemble the lens and the camera body it might not locate the lens on the camera exactly with the focus mark at the top. Example of mis-alignment with the Kipon adapter.

The mis-alignment isn’t an issue for focusing with the rangefinder.

LTM adapters that don’t incorporate 6-bit coding can be an issue because of the notch machined in the flange of the adapter. This notch exposes the optical sensor in the 6-bit coded M camera to variations in lighting. The variations in light causing the camera to “think” you’ve swapped the lens. The various lens modes on the M10 have different impacts when using this Voigtlander lens.

  • AUTO lens detect results in unpredictable interpretation by the camera. The results range from “no lens mounted” to the base default lens of 16-18-21 f/4.0 ASPH 11626. This is because the sensor is exposed to shadowing by you finger as you focus or any number of other things.
  • MANUAL lens setting can be set to whatever lens you are using, or an appropriate related lens. The issue remains that at times the camera will interpret a shadow crossing the sensor as mounting dis-mounting the lens. Generally when this happens, the camera switches to no lens mode. If you are rangefinder shooter, this might not be obvious to you. In LV view mode the camera puts up a warning screen “no lens mounted.”
  • OFF. This is obviously workable. The camera will function fine. You won’t get any EXIF data for the lens in this mode. Also, the camera will not perform any firmware correction for the particular lens mounted.

The absence of in-camera firmware corrections for lenses can be unimportant or a big deal. The lens that led me down this path, Voigtlander 21mm f/4.0 Color Skopar (LTM version), needs help from the in-camera firmware. If used without the Leica M lens selection set to 21 f/2.8 11134 you’ll get a magenta color fringe on the right side of the frame.

Magenta fringe along right edge of image. This happens with the Voigtlander 21mm f/4 Color Skopar LTM version when shooting without lens detection on M10-P.

Other Information about LTM adapters.

There is a good reference at Camera Quest that describes the various LTM adapters. There are definitely things to keep in mind when adapting the Leica thread mount to modern M bayonete with 6-bit coding.

Here is a discussion on l-camera-forum about adapting a 135mm Hector using LTM adapter.

< LTM Adventure II

LTM (LeicaThread Mount) to M-mount Adapter Adventure II

I finally received a Kipon LTM to M mount adapter with 6-bit coding. Everything goes together fine, however, there is a new wrinkle in the process.

Having an adapter that incorporates 6-bit coding alieveates the issue that required application of gaffer tape show in this blog post. You can see here the physical difference between an LTM adapter that has 6-bit coding and one that doesn’t incorporate it.

The segment that is cut out, illustrated by the RED annotations. On the Kipon adapter (right) the cut out is smaller to allow machining of the 6-bit coding on the back (camera) side of the adapter.
Shown here, the Beschoi adapter lying on top of the Kipon adapter. The 6-bit coding section on the Kippon is circled in RED. You can see the Beschoi adapter is machined away in that area.

This minor appearing difference is all the difference in the world if you are using a Leica with 6-bit coding.

The issue now is the fit of the adapter. Illustrated below the Beschoi aligns the mounted LTM lens pretty well with the camera body. On the other hand the Kipon has a good bit of misalignment.

Voigtlander 21mm f/4 Color Skopar mounted on M10-P using the Beschoi LTM – M adapter. You can see the RED mark emphasizing the alignment between the lens and the camera body. Pretty good, acceptable, I’d say
Same lens and camera with the Kipon LTM – M adapter. The RED marks help illustrate the amount of misalignment between the lens and the camera body.

The question is whether this mis-alignment is important or not. Based on the way that the focusing mechanism in the lens moves the rangefinder follower in the camera, this has no effect of focusing.

What causes the mis-alignment?

I measured the flange thickness of each LTM mount. By flange, I mean the part of the adapter that sits between the lens and M-mount on the camera body. The Beshoi is .05mm thinner than the Kippon. This is enough to change the alignment at assembly with the camera.

This saga, which in online forums is often trivialized “just get an LTM adapter” is much more trouble than you’d expect.

<LTM Adventure I LTM Adventure III >

LTM (LeicaThread Mount) to M-mount Adapter Adventure I

The LTM to M-mount world is a little more complicated than it used to be. Since 2006, when Leica implemented 6-bit coding, you don’t have to use the code, but your LTM adapter should cover the optical sensor anyway. If you’ve got an older Leica M-mount camera, this won’t be an issue for you.

It started with the search for a wide angle lens for my M10-P. To me, 28mm is about normal but on occasion a wider look is nice. The key is “on occasion.” That signals that the cost of Leica lenses isn’t warrented for this application. After noodling around the web, I came across the Voigtlander 21 f/4 Color Skopar as a really nice option. It’s super compact, just a little larger than the Leica 28 Summaron, which means it can go along easily without taking up a lot of space. Perhaps the perfect lens to provide the occasional wide angle perspective.

Taking the economics of this matter even further, while the M-mount Voigtlander is pretty economical (~$400) the LTM version used is about a hundred bucks cheaper. All you have to do is come up with a Leica thread mount to M-mount adapter. A used LTM version Color Skopar was located in Japan and ordered.

Next, get the LTM to M-mount adapter. After searching around Amazon and Ebay I found a couple of LTM adapter options. The M10 has 6-bit coding for the lenses, although it’s not required to use 6-bit coded lenses. You can manually input the lens from a menu in the M10. The first choice, a Kipon adapter which includes the machined pockets for filling in the appropriate lens code will take awhile to arrive. I ordered it and am willing to wait a little bit for it. At the same time though, my newly Ebay acquired Color Skopar didn’t want to wait. I ordered another, non-6-bit coded LTM adapter, this one by Beschoi.

When assembled onto the Voigtlander, the Bechoi adapter fit fine and everything seemed okay until the camera seemed to get confused thinking no lens was mounted when I operated the focusing ring on the lens. Fiddling around with the lens the realization struck that the optical sensor which is used to read the 6-bit coding on Leica lenses was exposed rather than covered by the lens mount. Every time I moved the focus ring the sensor would “see” my finger and think something had changed with the lens. The M10-P would display “no lens mounted” in the live view mode. If not using live view, it didn’t seem to be an issue; the fact that the camera doesn’t know what kind of lens is mounted aside.

For this particular lens, I want to used the M10 built-in lens corrections for 21mm, so it’s an issue for me.

The Leica optical sensor which detects the lens type is visible in this image. On the Leica mount between the lens serial number and the little focusing nub on the lens.
The LTM adapter mounted clearly showing the Leica optical sensor. The optical sensor needs to be covered by the adapter.

For the time being I installed a piece of gaffer tape to cover the sensor. That prevents the sensor from believing that the lens was swapped because the shadow of my finger crossed it while focusing.

Appropriate, even elegant temporary solution to the 6-bit coding sensor exposed.

LTM Adventure II >