Focusing E-Mount For Ultrafast Lenses

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There are a variety of old ultrafast lenses cheaply available. These lenses, usually marked between f/0.75 and f/1.6, typically have no aperture iris, no focus mechanism, and a giant external screw thread intended for mounting. They generally can't focus to infinity even on a mirrorless body, and IQ is scary soft, but sometimes that's a feature.... Anyway, I originally mounted these lenses by gluing an M42-to-A-mount adapter on the back (as I described in my Instructable, http://www.instructables.com/id/Using-Ultra-Fast-Lenses-on-DSLR-Cameras/ ). Instead, I've now built 3D-printable focusing E-mount adapters where the lens screws in using the large external thread (see 2nd photo) and can be focused by partial unscrewing. One mount has a 60mm thread that works with my Kowa 55mm f/1 and 42mm f/0.75; the other has an 80mm thread that works with my XR-Heligon 95mm f/1.3. The E-mount flange is a new design that should fit both older Sony E-mount bodies and the newer all-metal E-mounts (they have been tested with NEX-5 and A7II). In fact, the flange on the 80mm adapter has a different internal profile from the 60mm one, because the rear element of the XR-Heligon is huge and a standard-thickness E-mount could vignette. The last couple of photos were taken using the purple PLA adapters on an A7II and NEX-5. The kiwi was using the Rodenstock XR-Heligon and the princess ornament was using one of the Kowas. Note that the large flat on the adapters makes it difficult (but not impossible) to access the E-mount body lens release button and the 80mm adapter just barely clears the grip on my NEX-5, but the only way to avoid these issues would be to mount the lens farther away from the sensor, which would limit the focus range. The adapters print with the E-mount side up. This means there is a huge unsupported flat under the E-mount flange -- and that needs supports when printing. Both cura and slic3r had issues making good support structures, so I have designed-in a support that should simply be broken out of the center of the adapter after printing.

About the author:
ProfHankD
I'm a Professor of Electrical and Computer Engineering at the University of Kentucky, best known for things like having built the world's first Linux PC cluster supercomputer in 1994... although around the 3D-printing world I'm probably best known for my HingeBox (which Tested popularized). My research group (Aggregate.Org) really is about improving computing systems by making the various SW+HW components work better together, which we do for many different types of computer systems: supercomputers, digital cameras, ... and now 3D printers. I had some experience with tool and die making using Bridgeport Series I CNCs as far back as the late 1970s, but my 3D printing adventure started in late 2012 with purchase of a MakerGear M2 for my lab to make custom camera parts in support of computational photography research. I now use multiple MakerGear M2 and Wanhao I3 3D printers, several semiconductor laser cutters, a 3040T CNC mill, a programmable paper cutter, and a small vacuum forming machine.

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