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DIY Lens Mount Conversion of the Minolta Rokkor 58mm f/1.2 | by Arkku
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DIY Lens Mount Conversion of the Minolta Rokkor 58mm f/1.2

DIY Lens mount conversion, results (see below for "how to")


Here is the completed Minolta 58mm f/1.2 modification mounted on my Sony Alpha DSLR. Originally the lens is for the Minolta MC mount, which can not adapted to the Minolta AF mount "passively", i.e. any adapter would need to have optical elements to maintain infinity focus (at the expense of image quality). I managed to replace the mount on the lens itself by substituting an M42 to Minolta AF adapter for the original mount. After readjusting focus on the lens, it now aligns perfectly with the original distance scale, all the way to infinity.


While I did this for the Sony/Minolta AF system, the guide to the modification (see below) applies to any current DSLR system for which you can get a suitable adapter, e.g. an M42 to Canon EOS or a glassless M42 Nikon adapter can be used.


The lens was chosen because there is no f/1.2 lens available for the Minolta AF mount and most other f/1.2 lenses available tend to be either extremely expensive, hard to find, and/or far inferior (e.g., the Tomioka 50mm f/1.2 for M42 is not very good in my opinion). This lens, on the other hand, cost me about €100 and has bokeh worthy of legends. It is not the sharpest of lenses wide open (still, quite decent), but it has very pleasant image characteristics and is a lot of fun to use.


I recently updated this modification by installing a microchip which identifies itself as a 60mm f/1.1 lens (closest setting available at the moment). The chip was kindly provided by James Lao, who makes custom chips and M42 to Minolta AF adapters. If you use an electric adapter for the mount, the exact same guide can be used, or you can later install the microchip on the adapter (as I did).


With electronics the focus confirmation and in-camera anti-shake both work with this beast. (Focus confirmation doesn't depend on reported focal length, and for anti-shake the slight difference doesn't really matter that much.) The in-camera anti-shake of Sony DSLRs makes this a low-light photography marvel.


See the pictures beginning from here for my complete writeup on doing the modification. This method can also be applied to some other lenses, and certainly for converting to camera mounts other than Minolta AF.

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Taken on August 29, 2007