Spiratone CS-mounts and T-Mounts

I recently bought a Spiratone Expandar 28mm f/3.5 lens that was marketed as an M42 lens. Sure enough, it mounts

and focuses properly on M42 cameras. I noticed, however, that it appeared to have an adapter on it so I concluded

that it was actually a T-mount lens with an M-42 mount. So I unscrewed the adapter and found that the lens

mounted just fine on a T-mount for my Canon EOS (that is, it had a 42mm by 0.75 pitch on the rear of the lens

itself), while the camera to mount thread was, as stated, an M42 (42mm x 1mm) However, when I tried to focus on a

Canon body with a T-mount on the lens, the lens would focus to infinity only at its minimum distance, and would

not focus any closer than infinity.

 

I noted that the lens mount was actually marked CS, and I have another Spiratone wide angle (35mm) with the same

adapter. When I measured the "CS" M42 adapters, the distance from the rear of the lens to the front of the body

is in fact something like 9.53mm instead of the T-mount distance of 9.37mm. The M42 screws of the CS mounts (at

total=13.65mm) are also taller than on the true T-mounts (12.38mm).

 

I've googled <tm> both this site and generally, but all I can find that is even close is the much smaller

movie/astronomy lens mounts known as C and CS which have considerably different diameters and screwthreads.

 

I presume the Spiratone CS is a proprietary mount that was special for the Spiratone preset lenses, an in-house

variant of the more common T-mount. I do have some later Spiratone lenses (such as the 200mm) that are true

T-mount lenses.

 

Can anyone help me out here, and tell me if I've got it right or wrong?<div></div>

it does say CS, I thoughtb you were talking about the YS lenses, which were compatible to

T and T2, but had auto diaphragm.

I see from the photo that there is, indeed, a difference

the YS lenses were sold by spiratone as accura diamatic, Often or usually made by sigma.

they were also sold as several other brands including Cambron, ( i hesitate to mis-spenn the other names)

 

I read that later FIXED-MOUNT sigma lenses were actually YS lenses and the mounts could be changed.

 

I do not know how to is these lenses.

CS means "Contax Screw". That's who invented the M42 mount.

 

Sounds like they used a version with a proprietary register so that you couldn't use ordinary T-mounts. Who knows why.

 

Nice thing, you can just put a shim in-between the T-mount and your lens, and you should be able to get proper infinity focus. Won't need to be very thick, maybe 1 to 2 millimeters.

 

It's harder going the other way.

 

There's more than a few mount adapters that are just like T-mount, except for different threads, different register, etc. For instance, the Komura Unidapter uses diameter larger threads than T-mount.

John, I think you're right, of course about what the CS is.

- the CS is for the camera end and heaven only can guess what they called their slightly thicker version of the T-mount. I had not realized before that Spiratone's own mount was not simply a T-mount, however. The difference as I measure it is only about 0.16 mm, but it's enough to not be interchangeable. As you say, the T-mount is thinner, so a very thin shim might do it, although I'll probably just use these on the M42 cameras anyhow. On the true T-mount, the right focus is a little more than one full rotation out from all the way on the mount.

 

I looked through some of the ads Spiratone put out when they were still offering mostly preset lenses, but I can't see any offering of the mounts separately. Here's a price list from 1964 with the various mounts provided by Spiratone. Only Alpa cost more than the others.<div></div>

I've only had one Spiratone T-mount lens, a 400/6.3 that I bought new and still have; on a lens of that length,

the .16mm (about .006") difference would not be detectable. In fact, I wonder if that amount of variation would be

within spec tolerances for a T mount in any case? Surely it's not enough to be worth making it that much different on

purpose. I'm going to stick my neck out a little here and speculate that what you have is a pair of T mounts (maybe

or maybe not originally sourced from Spiratone, it would be hard to establish 40 years after the original sale), that ran

a bit thicker than another example. A tolerance range of +/- .003" might be unforgivably sloppy in a Nikkor, but

maybe not in a generic T mount.

It's not impossible, Richard (isn't it .06", not .006?), but I still suspect that this is intentional. The two

from the same kinds of

pre-set lenses are identical and differ from other Spiratone true T-mounts I have (like the one that came with my

400mm). In the advertising from the time these lenses were sold and in the list above, there is no mention of

adapters, just the list of mounts including Contax/M42, Exakta. Canon, and Nikon.

 

None of the fairly large number of regular T-mounts or T-mount lenses that I have (and Spiratone certainly

offered regular T-mounts as such later on like the 400mm lenses) are off this much or look the same as these.

This difference seriously affects focusing on the camera with both the 28mm and the 35mm lenses. They work fine

on the Canon with an M42>EOS adapter, but not with a EOS T-mount. Moreover, the Spiratone mounts marked "CS" are

thicker in the back of lens to the front of camera part, but are also longer and made differently on the actual

screw itself--there's a short gap with no threads between the threads and the base of the mount.

 

Well, thanks all. I appreciate your attention to my quandary.

No wait, it is .006 I see. Sorry- even as a math major in college I was challenged by conversions ;)<div></div>

0.16mm is a very small number, and much smaller (by about 500%) than the "one full turn" that you describe being required to bring the lens to proper infinity focus. I think the T mount system was pretty new in the early 1960s, maybe somebody made some lenses without having the correct specs for the mounts, and then Spiratone got them for a good price because of the mistake.....

 

:)=

Who knows, maybe so. Both lenses are clearly of the same vintage, although the 28mm was offered later than the 35mm.

 

Perhaps the difference between the measurements is in the gap in the screw threads. I think that my digital calipers are accurate, and I did the measurements several times.

 

Here's a 1965 Spiratone ad for the two lenses and a third, f/2.8, 28mm.<div></div>

<p>Much later.</p>

<p>The Spiratone 7mm fisheye may need a slightly different mount like these early Spiratone lenses to focus to infinity (<a href="../pentax-camera-forum/00TPgo">link</a> )</p>

<p>The Spiratone Auto 135mm f1.8 was actually made by Yoshida industries, not Sigma. The exact same lens was also sold with the following brandnames (that I currently know of): Polaris, Raynox Polaris, Carena, Beroflex, Samigon, Rokunar, Javelin, Raynox, Admiral and Automatik Weitwinkel...The Raynox brandname belongs to Yoshida industries. The lens was in production from 1973 up to 1978.</p>