RFSG » Leica M8 & 50mm F 2 Summicron DR

I have always been fascinated by the mechanical construct of Summicron50mmDualRange(DR). It was reputed to be a lens with very high resolving power as well. Unfortuantedly, it was listed as one of the “No.No” lenses in the M8 manual. This is because it cannot be mounted when set to the regular 1m – ∞ range, as the close focusing cam extends too deeply into the body and interferes with internal part of the M8 and may damage the M8.

There are 3 ways to use the DR Summicron on the M8, possibly M9 as well:
1) Send the lens to someone like DAG and machine the close focusing cam off for US$65 and using the lens only in the standard distance range, 1m to ∞, like a regular Rigid. This is unacceptable to me as it “destroys” the lens and negate the original intent of the lens for close focusing.

2) Optical Module DR & Rigid can be separated into the Optical Module & Focusing Mount by simply unscrewing.

So just unscrew the Optical Module from the DR and transfer to Rigid Focusing Mount and you can use it like a regular Rigid.
But it’s not so simple…. the Optical Modules of Rigid and the DR came off the same manufacturing line and the deign intent for both was 51.9mm as focal length. The DR mount being complicated and expensive to produce were only made for 51.9mm Optical Module. And of the 51.9mm optical modules that were produced, the better ones were said to have gone first to the DR, then to the Rigid. Thus all DR are of 51.9mm actual focal length.

And any optical modules that deviated from 51.9mm went to the Rigid Summicron. Thus the Rigid may have variation in focal length and you can’t mate the Optical Module and Focusing Mount of different focal lengths. The good thing is most Rigid are also in the 51.9mm range and also the focal length is hand-engraved on the barrel of the Optical Module.

So if you have a Rigid that is 51.9, you can swap with the DR. However, the alignment of the Aperture Index & Distance Index will probably be off. This will not affect the performance of the “hybrid” lens. Even if the focal length is not marked on the Rigid barrel, there’s no harm trying and see if it can focus properly after the swap since most Rigid are 51.9mm anyway.

3) Mount DR in close focus range with goggle and use it only in “Macro” mode. However, the black Bakelike leveling pin is in the way. Simply remove it and set the DR in Close Focusing range with goggle and then you can mount it on M8.