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Adapter to hold the 28 & 50mm Demi-C lenses on a Leica M39 thread (and have infinity focus).
Notes, the lens holding thread is very fine, some care should be used in fitting the lens to avoid cross threading.
Once in the mount, the lens helicoid should end at infinity as marked. The focus throw is quite limited on this lens, so undesirable to have the lens focus either side of infinity (or else you lose the close focus, which is around 1.2m/4ft).
However, it is very easy to adjust the lens collimation: loosen the 3 screws on the silver rim of the lens (furthest from the camera). Now the (black rim) front element will rotate until you see infinity in the viewfinder. Spin the silver ring around to line up the infinity marker, and re-tighten the screws. (These screws also allow the lens to focus closer or even remove the front element - don't unscrew too far!).
This is still a design in progress, copied and tweaked from a working print on a FDM/PLA printer, please take that into account, if a loose or tight fit!
Picture shows it on a GH4, via M43/L39 adapter, though perhaps surprisingly for a half-frame lens it does fully cover full-frame (with just slight darkening to the corners of 3x2 (Sony A7)).
[Aside: On the Demi-C the shutter and aperture are in the camera, but all the glass is in the removable lens. Some people have tried to remount them with the aperture assembly (destroying the camera), but it's not worth the effort: the aperture blades are not in the optical centre of the lens but behind the last element, this leads to severe vignetting as the lens is stopped down, which was less of an issue on half frame (and perhaps helped improve contrast by reducing stray light), but is useless on full frame where the lens is already darkening into the corners. The 50mm; wide open it has a little magenta fringing and (FF) noticeably soft outside the centre (which is pretty sharp).]