Voigtlander invented/bought many lens designs, including the well known Petzval, Heliar, Dynar, Kollinear, Skopar/Color-Skopar, Voigta, Zoomar, Lanthar, etc. I have accumulated a few of the original Voigtlanders and I enjoy all of them. Sure, there are challenges to get them to work with digital cameras, but the effort is well worth it. The latest addition is the Color-Lanthar 42mm f2.8, which came from a broken Voigtlander rangefinder. Unlike those lenses from the older folder cameras, this one was well bolted to the camera and it took some effort to remove it. Then it was not a small challenge to remove the shutter blades from the lens. Remember most old cameras have the shutter blades (like aperture blades) on the lens, instead of a focal plane shutter on the camera body in modern cameras. Without removing the shutter blades, they will completely block the light entering the lens.
The next step was to mount it onto the camera. The diameter of the lens is around 52mm. My usual way of securing the lens to the camera is using JB Weld to cold-weld the filter ring on the lens, and then the lens is screwed onto the focus helicoid. There is no difference with the Color-Lanthar, except it has a very short lens register, so short that even the 12-17mm focus helicoid is too thick. Fortunately, the lens has its own focus mechanism. As you can see from the second picture, I have a 52mm filter ring glued to the lens, and then a 52mm to 42mm step-down ring, and finally the thin M42 to E-Mount adapter. Works out really well for this lens.
Optical performance - I wasn't expecting the lens to be excellent, since the camera was consumer grade, and it turned out to be about that. Center sharpness is pretty good at f2.8, but the edges are muddy. Stopping down to f8/f11, the corners are markedly improved and is acceptably good. Of course there is more to a lens than just sharpness. I find the bokeh kind of interesting, and lens renders pictures with good details and tones.
To me, the larger part of the fun, is being able to use a lens to make pictures from a broken camera that's otherwise useless. Besides, lenses like this are very cheap. A new lens, however good or bad, is a good incentive to go out and shoot.
Color-Lanthar on the Sony A7. Looks pretty good, no?
Here you can see the lens with adapter is very compact. The front is the focusing ring. Not the easiest to focus but usable.
Waiting for the ice to be cleared by the Zamboni - Sony A7 & Voigtlander Color-Lanthar 42mm f2.8 at f8.
Bokeh - Kind of interesting, eh? Sony A7 & Voigtlander Color-Lanthar 42mm f2.8 @ f2.8.
Cold - Sony A7 & Voigtlander Color-Lanthar 42mm f2.8 @ f2.8, ISO 6400.
Lights - Sony A7 & Voigtlander Color-Lanthar 42mm f2.8 @ f2.8.