A curious Koike Auto Eye Hexanon KS 1.4/25

alex ph · Joined: 16 Mar 2013 Posts: 1662

I've finally got the potentiometer. How on earth its 5 pins should be connected to the three wires of the lens and to the power cell? Two side pins to the power, and the three others to the lens? And in which order?

visualopsins · Expire: 2025-04-11

Side pins are for mounting, typically ground...two outside of three pins are ends of the resistor; the center of three is center tap or "wiper". If the pot is linear taper (look it up) the outer two of the three pins connection order doesn't matter -- if pot taper is not linear, reverse connecting the outer two of three pins won't blow up anything, but turning the pot knob will result in sudden aperture movement near the end f turning -- in that case simply reverse the connections to the outer two of three pins.

alex ph · Joined: 16 Mar 2013 Posts: 1662

Thank you very much, Visualopsins! I'll provide myself with supplementary wire to conect both the battery and the lens, and will try to connect them all.

alex ph · Joined: 16 Mar 2013 Posts: 1662

I adapted the lens to E-mount and now I have a wired Nex Koike Hexanon (sounds pretty, right?).

Some closeup test shots with Sony Nex at arbitrary aperture values:

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#3 simple BW conversion

Formally speaking, the adaptation is simple - if you have minimally fit equipment. I unscrewed the bottom plate, as shown in previous posts, and replaced it with a M42 to Sony E thin adapter ring.

To do this, I had to mark the future holes on M42-E adapter through the holes of the original bottom plate and then drill the M42-E to let the original screws be reused.

First issue, I have a drill with 12V accumulator battery which works better as an electric screwdriver. Drilling even a thin metal surface of the M42-E adapter was not a great success. I just broke a couple of drill bits. So to perforate the holes I used a... nail and a hammer. That gives initially ugly and raw inlet. Than I used three drill bits of various sizes to enlarge and polish the holes. It worked almost OK. As the work was far from being precise, I could only screw in three of fours screws. Let's say it is not the worst result for the purpose.

Besides, when hammering the adapter with a nail, I slightly bent the adapter. So some levelling was necessary, with help of pliers, in order to let the adapter sit back on Sony Nex mount.

I also loosended the retaining screw on the lens in order to let it focus closer. My hope was to be able to get focus further, at infinity. But for this, I suppose, I need to file the focsing ring which I don't dare to deal with for the moment.

I still haven't managed to attach the electric part in order to control the diaphragm on regular basis, in spite of the first promissing signs. So, the total adaptation takes a long moment, longer than expected. Classic!

What I have now is a character lens with max shooting distance of around 2.5 meters and min of around 5cm (before the lens drops out of the helicoid). The max shooting distance kind of puzzles me because the original metal plate in the lens bottom looks thicker than the M42-E adapter. And when I was strongly pressing the original lens against Sony mount, I could shoot at a longer distance. In terms of minimum shooting comfort ad lens safety those two ways are incomparable, so I am glad to have a new unusual portrait and close-up lens. And the adaptation is entirely reversible, just in case one day I decide to turn the lens back to security video circuit Laughing

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kathala · Joined: 13 May 2022 Posts: 141

alex ph · Joined: 16 Mar 2013 Posts: 1662

Thank you for your cheer up! That makes me pleasure in this Auto Eye adventure.

You make an interesting allusion to MF feeling. I did not look at the taken pictures in this way, redundantly attached to the idea I was using a small CCTV lens. It does not even seem to have a large field curvature, instead it doubles shapes in OOF zones.

What is also curious in its rendering, it does not distort edges, unlike many other CCTV and projection lenses, but just "cuts" the image circle with a minimal distortion. That does not owe to the C-mount as I removed it when changing the plate, and the result is precisely the same. This makes me think that with a larger rear glass this lens could cover a significantly larger sensor.

I experimented more with the newly adapted version and found out that max focusing distance is larger than I thought before. It comes to 5 or even 10 meters and with the aperture closed almost reaches infinity.

Here are some more samples in open air, exposure and contrast tweaked.

Close range, with the internal "eye" imprint most visible in this kind of shots

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Mid range

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Far field

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P.S. For the moment I mostly like the hard vignette which adds even more character, so did not make cropping.

alex ph · Joined: 16 Mar 2013 Posts: 1662

A bit more close-ups taken with this unusual lens.

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alex ph · Joined: 16 Mar 2013 Posts: 1662

Finally infinity and problemless near infinity shots! I found out that previously the helicoid was simply making a very tough last half turn bringing the lens to an intermediary position rather than to its deepest point within the barrel.

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