Helicoid Adapter

March 25, 2012

The popularity of the mirrorless systems from Sony, Olympus and Panasonic has led to a soaring number of adapters to fit all sorts of lenses. The NEX (E-mount) for example, has adapter mounts for different DSLR brands, rangefinder lenses (M mount, LTM mount), and legacy lenses. Many users, like me, are attracted to rangefinder lenses to accompany the small NEX camera. Certain rangefinder lenses (the Zeiss biogons for example) have the rear elements protruding far inside the camera body, so naturally they cannot be adapted to DSLR bodies since the lens would be hitting the mirror. On the other hand, rangefinder lenses can be easily coupled with the mirrorless cameras, thus reviving the use of old legacy lenses on new digital bodies. Together, they form a flexible and portable solution, but the compromise is you lose the ability to autofocus and in-camera lens correction. Personally I find manual focusing an enjoyable experience.

This article is to demonstrate the use of an M-to-E mount helicoid adapter on the NEX. It serves two purposes: (1) when in its natural configuration, the adapter connects an M-mount lens to the E-mount body; (2) it can extend itself via a helicoid ring by around 5mm and is essentially a macro extension tube. Rangefinder lenses from companies like Leica, Zeiss and Voigtlander usually have a relatively long minimal focusing distance, thus making close-up photography unfeasible. With this helicoid adapter, the extra length of the adapter in its extended position allows closer focusing. Theoretically the photo quality deteriorates because there is less light entering the sensor and the corners of the image are particularly affected; but in real life the effect is acceptable.

I tested the combo with my Voigtlander Nokton Classic 40mm f1.4 (M-mount) on NEX-3. The first picture shows the helicoid adapter in its natural collapsed position, it allows the lens to manual focus natively from 0.7m to infinity. I set the lens to its minimum focusing distance at 0.7m, you can see it focused on the wooden floor far away from the objects in question. Then in the second picture I turned halfway through the adapter, and it allows closer focusing to bring the more distant objects (the silver lenses) into focus. The last pair of images demonstrates a full turn of the helicoid to the extended position and now the lens can focus on the close subject (the flash) at 0.3m.