Focusing E-Mount For Ultrafast Lenses

myminifactory

There are numerous old ultrafast lenses available at an affordable price. These lenses, typically marked between f/0.75 and f/1.6, usually lack an aperture iris, a focus mechanism, and feature a large external screw thread for mounting. They generally cannot focus to infinity even on mirrorless bodies and have IQ that is surprisingly soft, but sometimes this is a desirable feature. Anyway, I originally mounted these lenses by attaching an M42-to-A-mount adapter to the back (as described in my Instructable, http://www.instructables.com/id/Using-Ultra-Fast-Lenses-on-DSLR-Cameras/). Instead, I have now created 3D-printable focusing E-mount adapters where the lens screws in using the large external thread 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; another 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 on NEX-5 and A7II). In fact, the flange on the 80mm adapter has a different internal profile than the 60mm one because the rear element of the XR-Heligon is enormous and a standard-thickness E-mount could cause vignetting. The last couple of photos were taken using the purple PLA adapters on an A7II and NEX-5. The kiwi was shot with the Rodenstock XR-Heligon and the princess ornament was captured with 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 facing up. This means there is a massive unsupported flat under the E-mount flange – and this needs supports when printing. Both Cura and Slic3r had difficulties 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.