Tim Isaac's M-Coder

Leica Jan 16, 2008

In the world of rangefinder photography, the name Leica is revered. Creators of the 35mm film camera, this German camera maker is well known for its optics and build quality.

In late 2006, Leica introduced the M8 – the first digital camera in the M-series. With it’s minimalist Bauhaus design, solid construction and the ability to use almost any M-mount lens made since 1954, Leica had a winner in its hands. Granted, the product has its quirks (like requiring the use of UV/IR cut filters to prevent black synthetics from looking magenta, or having to shoot RAW all of the time due to a weak JPEG conversion engine) and it is a mostly manual camera (no autofocus and aperture priority is the only “auto” mode), but it has been accepted as a true marvel by the rangefinder community.

One of the more ingenious ideas Leica had in developing this camera was coming up with a system to identify the lens mounted on the camera for EXIF data and (in some cases) in-camera vignetting correction and cyan drift adjustment. By adding a 6-bit code consisting of black and white dots painted on the mounting flange of the lens (in tiny little pits milled into the flange) an IR sensor on the camera body can then “read” the lens and make the appropriate adjustments. Leica will retrofit any compatible Leica lens with a 6-bit code for a small fee.

However, Leica would only do this for its own brand of lenses. The rangefinder community was justifiably upset about this. Lenses by Carl Zeiss and Cosina Voigtlander which were perfectly usable on film-based Leica M’s were left out in the cold. It was in the midst of preparations for seppuku, when a clever Leica owner noticed that marks made by certain black permanent markers could be read by the sensor. Thus began a quest to come up with a method to code non-Leica lenses using permanent markers accurately.

This is where our hero, Tim Isaac, comes into the story. An engineer and CAD specialist, he had already made a name for himself in the Leica community with the development of his Thumbs Up grip adapter for the M8. Applying the same rat cunning to the problem of accurately marking lens codes, he developed his M-coder System.


The kit consists of a sturdy plastic tool (the M-Coder) that serves as the guide for placing the marks on the lens flange. The tool is keyed to the alignment holes on the flange so it is very easy to place correctly. Next is a guide wheel to tell you what codes to apply to the lens (the D-Coder). Lastly, Tim’s kit provides you with a Japanese Zebra industrial marking pen that writes well on metal and can be read by the sensor on the M8. Finally, the whole thing is neatly stored in it’s own carrying case (complete with CAD images of Tim’s lenses).

I tried the M-Coder on my newly acquired Zeiss ZM 50mm Biogon f/2. The lens is M-mount, so it’s compatible with my Leica M8, but cannot be coded by Leica as it is not a Leica brand lens. I slipped the M-Coder onto the lens mounting flange, checked the D-Coder for the appropriate code, (I had to surf to http://www.digital-leica.com for a lens compatibility list), and using the Zebra marker, added the two black marks needed to convince my M8 that I had just mounted a 50mm Summicron IV f/2 lens instead of the Zeiss. A couple of test shots later showed 50mm in the EXIF data confirming that the marks were successfully read.

Tim’s documentation states that his kit provides temporary lens coding and that is correct. Considering the tight tolerances between the lens and body flanges, I would expect the marks to come off after 3-4 lens changes. In order to make this permanent, you need to send the lens flange off to be milled. Neither Zeiss nor Cosina offer this service, but there is a gentleman named John Milich who will do this work for you for a minimal fee. The only catch is that you have to remove the flange yourself and mail it to him. When he sends it back (John generally has a 1 week turnaround) you will have to remount the flange yourself. The complexity of this task varies from lens to lens. I have done this on two of my CV lenses (40mm Nokton & 25mm P Color Skopar) and one was much simpler than the other. YMMV. You can reach John by e-mail and his address is jm at milich dot com. Tell him that I sent you.

In conclusion, Tim Isaac proves once again that he is the “go to guy” for designing gadgets for the Leica M8. His current projects also include a “coldshoe” version of the Thumbs Up (with one or two coldshoes) and a new battery charger for the M8. Tim’s website is http://www.matchtechnical.com and you can e-mail Tim at TimI at matchTechnical dot com.

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