[Focusrite]

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Hi all. I recently succumbed to LBA and came into the possession of a nice old Sigmatel 135mm lens with a Y/S mount on it. The previous owner had a Nikon F NAI mount on it, and used it with a Micro 4/3 camera with an adapter. I was under the impression that the Y/S mount is very similar to the T-Mount, and that adapting it to M42 or K mount ( preferred ) was a simple affair.
However, after doing a bit of searching ( hopefully in the right places?? ) for information and talking with a gentleman who ( apparently ) unsuccessfully tried to adapt a similar lens, I'm a little bit worried that it might be a bit more complicated and a little less feasible than I had originally thought. I'm not overly concerned about retaining infinity focus, as the lens would be used as a portrait lens; and neither am I concerned about keeping the function of the aperture level. However, if it is as simple as purchasing one of those cheap T2/K mount adapters and swapping the plate on the back? Or do I have to find an original mount for that lens to suit K mount, or a vintage adapter that's rarer than hen's teeth?
If I've goofed, you're more than welcome to tell me; but if adapting it is indeed simple I would appreciate any information that people may be able to provide, especially if lens surgery is involved!
Thanks in advance.

Attached Images

     

[PJ1]

I thought Y/S was a threaded mount like the T mount but with the addition of an aperture pin. This is a bayonet mount and I can only think it might have been confused with Contax/Yashica C/Y? No doubt someone more knowledgeable than I am will know.

[Focusrite]

I don't know about it being a C/Y lens mount; I'm thinking that it is possibly an original-ish Nikon F NAI mount ( complete with bunny-eared aperture tracker! ) that has been mounted on the threaded Y/S.

With a bit more of a closer look I have discovered another couple of details. It appears that it does have an aperture pin as you mentioned ( shown on the right side of the photos ), however it's held down underneath a ring that runs around the circumference of the barrel and is hinged on the other side of the lens. The prominent aperture lever ( left side of photos ) simply controls the position/height of the ring; pressing the aperture lever raises the ring and allows the aperture pin to extend as well.

I'm feeling a bit more confident about it now. Hopefully it's just a case of unbolting the Nikon mount somehow, which should allow a normal T-mount adapter to go on.

[boriscleto]

Attached find a manual for YS lens adapters (one of the less common interchangeable lens mount systems which is basically a T mount with a Pentax screw mount like stop down pin added). This interchangeable mount system was developed by Sigma as competition to the Vivitar/Soligor T4 lens line and the later Vivitar TX line. It was used on some Sigma, Lentar, Upsilon, Accura and Spiratone lenses along with a few other brands. The simpler models without open aperture metering are very simple to install compared to the more touchy T4 and TX adapters (usually just a matter of screwing them on the lens). It was not until I saw this instruction book that I realized some of the open aperture metering models have very complex installation instructions. I recently received this with a still-in-the-box YS adapter (along with a little screwdriver they apparently originally supplied with them). It is in html except for 4 photographic illustrations. It might be helpful to some people to post this because the instructions for installation on some models, particularly those cameras with open aperture metering, are surprisingly complex (the ones I have used are among the more simple ones to install usually being about as complex as installing a T mount adapter) and the bulk of YS adapters around were probably separated from their manuals long ago. The information available on the web regarding this mount system is very limited.

YS Interchangeable Adapter Mounts

YS Adapter mounts are available in models to fit most 35mm SLR plane shutter cameras. They fit any YS lens to the particular camera body to provide full automatic operation of the lens diaphragm and meter coupling where appropriate.

All YS adapter mounts (and lenses) have the identical specifications as T Mount lenses and adapters so that T adapters may be used on YS lenses for those cameras for which no YS adapters may be available. Naturally, with T adapter the operation of YS lenses would be non-automatic.

To mount or dismount a YS lens on the camera body, it is best to grasp the YS mount rather than the lens barrel itself.

YS Interchangeable Adapter Mounts, Y-S lens mount

[Focusrite]

Thank you! That was perfect, and mercifully quite simple. The mount has been removed, and indeed there is a dovetail on the end of the lens. I have a T-mount adapter, but unfortunately the dovetail is larger and shallower than the adapter, so I'm going to have to machine the inside diameter of the adapter out and drill/tap out new holes for the holding screws. I've ordered a couple of extra T-mount adapters ( the inexpensive type ) in case I ruin it! And you never know, maybe one of the adapters will have the correct diameter. I won't have access to a lathe for a week or so, however.

I may need some guidance with the correct flange distance in case I need to or should machine the mounting face of the adapter down as well. The adapter is taller than the Nikon mount by a little over a millimetre. I understand the Nikon F mount register distance is a little more than a millimetre over the Pentax K ( 46.50 vs 45.46mm ), so that means that I should shave around 2mm off the adapter? Or do I have that backwards? It would be a bonus to keep infinity focus.

[PJ1]

You are correct. Pentax registration distance (M42 and K Mount) is 45.46mm. Nikon F is 46.5mm. So I believe the Pentax mount would have to be 1.04mm longer than the Nikon F mount measured from the rear face of the lens to achieve infinity focus.

[ABBANDON]

Having just recently rescued a 135mm F1.8 Sigmatel too but without a mount I was looking for solutions too, you can use it with an applicable T2 mount but the aperature will remain open. I got my lens in a local charrity shop and the guy who deals with cameras is quite knowledgable and claimed that he has this lens too and found it relatively simple to remove the lens backplate and disable the auto aperature mechanism.

I haven't done this myself as after a bit of persistance searching ebay I brought this purely for the ys-PK mount on it hopefully should arrive soon.

The links to info on the YS mount don't mention PK as an option but it seemed inconcievable that there had not been one made by someone although this page sugests they are quite rare

I'm now currently looking around for a Nikon mount too as I have Nikon as well as Pentax cameras but so far have only found ones attached to expensive lenses.

There is a review in the lens database this has some more information on the lens. My copy came complete with hood caps tatty box and all the original papers which include a bit more usefull info which hopefully I'll will get round to scanning and adding some where usefull.

I am also going to visit a couple of my favourite UK seconhand camera shops soon and have a look for YS mounts I get the feeling that for most of the bigger dealers it just isn't something they see or would be bothered with.

[Focusrite]

Using a mount off another lens is a good idea; especially if it lets you keep the use of the aperture. I ended up modifying a T2 adapter, machining out its internal diameter and then drilling and tapping six new holes for grub screws low enough to actually grip in the recess of the dovetail. I also machined up a shim that now sits in the gap between the adapter and the lens and holds the aperture pin down, so it's a fully manual lens for me, but I can at least use the aperture

I'm still a little nervous about having such a large and heavy lens supported by six grub screws resting against a dove tail, but the lens was originally equipped with only three so hopefully it'll be okay!