Yashinon Auto 55 1.8

[kenetik]

Inspired by Old Hand's lovely Yashinon DX 50/2 set, I asked a few questions and started wondering about the Yashion 55 1.8 I have. I have never used it, didn't know what mount it was. Casual Collector clued me into the fact that it was a Pentamatic mount, something I don't think there is a commercial adapter for.

Anybody DIY adapted or converted a pentamatic? The lens is beautiful and heavy and the glass is unmarked and clear. I saw some shots in another thread with this lens, I think in M42, and they were really nice.

I put an M42 adapter around it to shield the bayonet and held it to my camera. This created a small extension tube effect, and I really liked what I saw. A few wide open, a couple stopped down to f4 or so.

[Oldhand]

Looks like a very good lens - no surprise there really.
You have some excellent results from your DIY mount.
If a more permanent solution can be found you will have a most useful image making tool.
Thanks for sharing
OH

[bhargav]

Nice results. In the first you almost have a tilt shift adapter effect, cool!

[Univer]

I recently had occasion to deal with this very question. I purchased (in full foreknowledge of the mount) the 5.5cm/1.8 Pentamatic Auto Yashinon. My plan was to use what I've come to call my "universal" adapter to adapt the lens to a short-register mirrorless platform. The "universal" adapter is simply an old M42 T-adapter with the inner ring removed and longer screws substituted for the original grub screws. In combination with a short M42 adapter (intended for use with a focusing helicoid) and some combination of M42 rings/tubes/helicoids, it has proven remarkably useful over the years.

I also had the Quixotic hope that I might be able to use an existing "proper" adapter with this lens; I had read online comments suggesting that Minolta SR might be a possibility.

Unfortunately, the Pentamatic bayonet mount is rather wide - fractionally too wide to fit inside the outer ring of the T-adapter. And I had no luck using any other adapter; I have most of the usual suspect adapters available, and I tried them all, without success.

In the end, even though I normally resist non-reversible/destructive lens modifications, I decided to take a radical approach here. (I don't own a Pentamatic body, and the chances of my ever owning one are remote.) Using a rotary tool, I carefully ground away the bayonet flanges - a matter of fifteen minutes' work. The lens now fits comfortably in the "universal" adapter. Using a short M42-to-Sony-E adapter plus a ~10mm M42 extension tube yields a focus range very close to the factory markings. (Note that I haven't yet thoroughly tested infinity focus.)

A few hasty snaps suggest that the Pentamatic lens is very good indeed. A related note: on the basis of a quick side-by-side comparison, I believe that it may be optically identical to the later M42 5.5cm/1.8 Auto Yashinon - not the semi-automatic 5cm/2 lens that immediately followed the Pentamatic mount, but the next generation after that: the first of the fully automatic M42 Yashinon "normals." So for anyone interested in the performance of the Pentamatic lens, it may be that the later M42 lens offers a more readily adaptable way to experience it.

Hope that's somewhat helpful. Best of luck with the lens!

[kenetik]

Univer,

Thank you for the response. I know the minolta is only fractionally different regis than the pentatmatic mount, but discovered as you did that the pentamatic mount is indeed very wide. I would love to see some pics of your work on the mount and how it fits into your universal adapter. The lens seems to be a very sweet optic indeed.

Thanks for the info.

Ken

[Univer]

Hi Ken,

I'd be happy to snap a quick photo or two. The adaptation work isn't particularly artful, but hopefully the images will be of some help.

Stand by - photos to follow shortly.

Cheers!

[kenetik]

Great. Before I take a grinder to the lens, I want to see if I can replicate your setup, including your universal adapter!

[Univer]

Hi Again,

Sorry to be so slow to reply. Here are a few hasty snaps, dust and all; hopefully they’ll give you an idea of how this homemade contraption works.

Picture 1 shows the lens alone, with the bayonet flanges ground away. Not my neatest job, but far from my worst. I carefully masked off every surface other than the one I was working on, and did my best to remove metal just until the bayonet area was even with the area around it. Probably better, in this case, to err on the side of removing less rather than more; I don't think it's strictly necessary to grind the flanges away completely in order to get the lens to fit in the adapter.

Picture 2 shows the adapter alone: the outer ring of a standard M42 T2 adapter, with the inner ring removed. Three longer screws have been substituted for the original grub screws. I simply brought the adapter with me to the local hardware store, and tried various screws until I found the correct size.

Picture 3 shows the adapter in place on the lens. The screws have been tightened to hold the lens securely (sometimes it’s a bit fiddly to get the lens properly centered in the adapter, so as to avoid an unintended “shift” effect, but that’s not a huge issue).

Picture 4 shows the M42 extension tube added to achieve something close to the proper register length; this will vary, of course, depending on the camera system and the depth of the “short” M42 adapter being used (the sort of adapter intended for use with a helicoid focusing tube). It's helpful to have a few sets of extension tubes available; in this case, the best choice turned out to be Tube No. 1 from a set of Mamiya/Sekor branded tubes.

This is a fairly flexible adaptation method. As long as the rear flange of the lens will seat flush against the inner “shoulder” of the adapter, it should work reasonably well. And in the great majority of cases, no irreversible lens modifications are required.

In practice, I find that I need more than one of these adapters; I have a second one with longer screws, for skinnier lenses. Note also that there’s some variation among T2 adapters in terms of the precise placement of the three screw holes: some are higher and some are lower, and a small difference in this respect can make a significant difference in the screws’ ability to tighten securely against the lens. This is very much a trial-and-error, adjust-as-you-go system.

There’s nothing magical about the M42 part of the T2 adapter; I chose that mount because it was easy to find M42 helicoid tubes and short-register “helicoid” adapters.

As noted previously, this sort of adaptation should work very well for any of the short-register mirrorless formats. But given the Pentamatic register distance, this setup would afford only close-up focusing with a conventional SLR.

Again - I hope this is at least marginally helpful. Best of luck with your lens!

[Lloydy]

I like your thinking....an easy solution to the problem.

[kenetik]

Univer, thank you for taking the time to show how you modified the lens and your universal adapter. I am going to try something similar soon. I love the adapter, it's a great solution for multiple registers. Thanks again, I will post my results soon.

[Univer]

@ Lloydy and kenetik: thanks for the kind words. It's a distinct pleasure to pass along the information - acknowledging that this is a rather inelegant and rudimentary technique. But it has been surprisingly useful, and has enabled me to mount any number of "unadaptable" lenses. I hope it does the same for you!

[Lloydy]

I'm now looking at the mint Vivitar 28 / 2.8 Close Focus that I'm struggling to sell because of it's Konica mount in a completely different light. Get the Dremel out and be damned!