Using a Focusing Helicoid as a Lens Adapter

One of the most annoying problems with old manual focus lenses, is that over time, some of them would fail to attain infinity focus, due to wear or misalignment. The Vivitar 24mm f2.8 TX lens I looked that the other day was an example. The normal course of action is to get it repaired/adjusted, but this could get expensive. Worse, sometimes after a lens repair, it would have other issues like de-centering or other problems. The solution is to use a focusing helicoid in place of a lens adapter.

Helicoid as an adapter on NEX-5N. Click for larger.

My focusing helicoids were originally purchased to be used with odd ball lenses that don't have focusing mechanisms of their own, like enlarging and projection lenses, but they are equally good, and often better, when used as a lens adapter, because a focusing helicoid would make the lens focus closer than its minimum focus distance, but at the same time allows the lens to focus past infinity. The 18-35mm Yeenon helicoid is just slightly thinner than a dedicated NEX to M42 adapter when not extended. This means all M42 lenses mounted on it will focus pass infinity. This solves the problem for lenses that can not focus to infinity by itself.

Allen Garden - NEX-6 & Vivitar 24mm f2.8 TX & Yeenon Helicoid. Click for larger.

Currently, I can only use M42 lenses on the Yeenon Helicoid, as the helicoid has an M42 mount when fitted with a 52mm to 42mm step-down ring. In actual use, there is almost no different than using just a lens adapter, except you focus with the focusing helicoid or the focusing mechanism on the lens. When using the lens for close-ups, you can rack out the focusing on both the helicoid and the lens to simulate the effect of  an extension tube to achieve macro magnification.

So yes, the helicoid is a very flexible tool.

True Love Cafe - NEX-6 & Isco-Gottingen Westagon 50mm f2 & Yeenon Helicoid.

The Transplant

I have had this ISCO-Gottingen Westagon 50mm f2 lens for many years. This lens has an M42 mount and is considered a cheap version of the Schneider equivalent. One problem with this lens is that it has haze inside and it produces washed out, hazy pictures with no contrast, so I never really used it. At one of the photo shows last year, I bought a broken (aperture), but an Exakta mount of the same lens. The Exakta version has very beautiful fit and finish, but the aperture is broken and I can't figure it out how to remove the aperture blades and fix it. The optic appears to be cleaner than the M42 version.

Most old lenses have optics in groups that can be removed very easily. In this particular lens, it has the front and the rear group. Despite the different looking lens barrels, the optical element groups are identical in both lenses. Took the optics out from the Exakta mount lens, and put them in the M42 lens barrel.  Works beautifully.

The lens itself isn't too bad. In fact, it's quite nice. A bit slow with the f2 maximum aperture, but can't complain about the cheap price of $5.

Left shows dismantled Exakta mount of the lens, right shows the transplanted M42 version

Street Crossing - NEX-6 & Isco-Gottingen Westagon 50mm f2. Click for larger.

Umbrella - NEX-6 & Isco-Gottingen Westagon 50mm f2 @ f2.8.