A Mystery Lens

Scrolling through eBay, I stumbled upon a listing titled,

Unknown Prime Lens with f/2.0 Maximum Aperture with Unknown Mount

Immediately, I was enticed by the wide maximum aperture. Even without knowing what it was compatible with (if anything at all we have here at the office), a lens with a wide maximum aperture allows for some flexibility. With how much light it lets in, we can always stop down, but getting more light from a something closer to a kit lens or something with a max of f/5.6 or f/8 would require at least three stops to get up to f/2.0.

Going off of pictures, the mount didn't immediately resemble something I was used to, so I wondered if maybe this was a custom conversion job. I looked like it used a breech lock mount, as opposed to a threaded mount or bayonet mount. PL was ruled out, because of the amount of prongs, but a three pronged breech lock mount made me think Pentacon 6, B4, as the pictures didn't do me any favors as far as scale went.

Well, Fotodiox always loves a challenge, so it was a purchase without much more thought. Fast-foward to receiving the lens, it's a cute little prime. Now that it's in my hand, it's far too small to be Pentacon 6. B4 was my next best guess, so I grabbed a B4 adapter, and thankfully, that was the case.

With the built-in tripod foot, the setup feels robust, and mounting is smooth. It feels like a rig ready for video and filmmaking. After testing, I found it wouldn't be that easy.

With the lens set to infinity, here's an image I got when I walked outside. When the image is this out of focus, it has to be drastically far from the sensor or close. If I move the lens closer to a subject, I'm eventually able to get something in focus, so the lens is definitely too far from the sensor.

If anything, we have a compact macro lens. The image above is the farthest we can focus. If we focus down to the minimum focus distance, here's what we can get instead:

The out of focus characteristics of the lens are smooth and pleasing to look at, and it's good to know the lens isn't completely unusable. Curiosity has me wondering if there's a way we can mount this to allow for infinity, but that'll be a project for a different day.