t-mount adapter question

agnosticnikon · Apr 10, 2013

While on vacation, I picked up a few odds and ends in antique/junk stores, and found an cheap old Soligor 100-200mm pre-set lens. It has the spiffy chrome and black striped focusing, aperture, and zoom rings, so I had to have it. It has a Petri t-mount with rear cap that screwed off easily. But when I went to put a Nikon t-mount adapter on, it wouldn't screw on . I tried several t-mount adapters I have for other lenses, and none of them worked. One of my older ones started to take hold, but jammed after maybe one turn. I know that t-mounts have a 42mm thread size, so I measured the thread size on the lens, and it looks to be about the same, including the thread pitch, but it seems to be just a little too big for the adapters. (I don't have anything more accurate than a steel drafting ruler) The threads don't appear stripped at all either. So I don't know what's going on here. Were t-mounts ever made in other sizes, like 43mm? I have never seen a pre-set lens use anything except a t-mount adapter.
Anybody have any experience with these things? Any help would be appreciated.

randyB · Apr 10, 2013

In the early days (50's/60's) of SLR lenses by independent lens makers there were several versions of the T-mount type mount. I have several that don't fit any T-mount lens I've owned. Finding what you need may take a while.

agnosticnikon · Apr 10, 2013

randyB said:
In the early days (50's/60's) of SLR lenses by independent lens makers there were several versions of the T-mount type mount. I have several that don't fit any T-mount lens I've owned. Finding what you need may take a while.

Thanks for the help. I figured it might be something like that. Hard telling where I might find an adapter. It would probably be easier to just buy an old Petri if I wanted to use it.

rjbuzzclick · Apr 11, 2013

It might also be a Miranda screw mount. My Miranda G has a bayonet mount, but the inside of the mount is threaded as a screw mount. I have one Soligor 135mm preset lens in this mount. I believe it's 43mm diameter threads.

Yashinoff · Apr 11, 2013

Miranda threads are a lot coarser than what's on a T mount. What we generically refer to as a T mount, is more specifically known as a T2 mount and didn't come about until 1962. There are earlier "T mounts" which are slightly different. (edit: or so I thought - apparently the only difference between the T mount and the T2 mount is the T2 has set screws in it so you can orient the lens properly in the mount. But some lens manufacturers had proprietary mounts using the same principle)

noacronym · Apr 11, 2013

I've bought enough old cameras to where something like some side-market zoom lens comes with it, I do the world a favor and throw it in the garbage. As a teenager in the early 70's I'd only daydream about owning one. That's one thing I never threw my money away on though. So if you're holding that lens in your hand, I'm certainly not culpable. So take heart, you can put THAT lens out of your mind by the nearest wastebasket.

rjbuzzclick · Apr 11, 2013

Ah...I believe that I misunderstood what was being talked about previously. You're talking about the thread size that goes between the lens and the mount. I have a few lenses branded by Soligor and Vivitar that use a setup like this so they can build one lens to fit several different mounts. I never knew what they were called. Mine all have the set screws to properly orient the lens too. Thanks for the clarification. Unfortunately, I can't tell you what the thread size is. I've attached a photo if that's any help to anyone.

Yeeski · Apr 12, 2013

Earlier Petri SLRs used a proprietary bayonet mount before they switched to the M42 mount. This is a wild guess, but maybe you have an M42 mount lens with a Petri bayonet mount adapter attached. The following link might be of interest:

http://mattsclassiccameras.com/petri_vi.html

David Lyga · Apr 12, 2013

This madness is why, early on, with every camera show I attended, I would rarely refuse to buy cheap 'adapters', of all sorts, for 'just in case' reasons that would somehow manage to manifest in the future. - David Lyga

AgX · Apr 12, 2013

But aren't those scenarios above those "just in case" situations?
I guess it all depends on the price of those dapters. And the room one got...

agnosticnikon · Apr 14, 2013

I'd like to thank everyone for their comments. But I have somewhat solved the problem. I unscrewed the set screws on the Petri t-mount and an old Nikon t-mount I had, and removed the center piece with the t-mount threads. I saw there was little difference in in the size of the rings, so with a little grinding and filing, I got the thread ring from the Petri mount to go into my Nikon mount. I tightened up the set screws and threaded it back on the lens, re-set the screws to center the lens, and there we go, mounted perfectly on my old Nikon FTN. One leetle problem; the lens won't quite focus to infinity on the camera. It's good to about 25ft. or so, then that's it. I may work on this problem some more, or just use it for closer subjects.
Life's a learning experience, no?

AgX · Apr 14, 2013

Both, the bad fit and the lack of infinity flange-film distance show that the T-Mount is rather a principle employed by several manufacturers than a universal system with complete interchangibility.

rjbuzzclick · Apr 14, 2013

In the OP's case, I would say that he got two things to fit together, by grinding and filing, that weren't meant to fit together, which is why infinity is off. The pieces that I have (previously posted photo) do all fit together quite well, and the mount adapters are different depths so there is infinity focus with the same lens on different mounts. However, I'm not clear as to if what I have are called T-mounts, or something else.

agnosticnikon · Apr 14, 2013

The saga continues. My modification of the t-mount shouldn't have had any effect on the focus, because I only removed material from the circumference of the threaded insert. Both the Petri and Nikon adapters measure the same thickness, although the Petri bayonet and Nikon bayonet mounts are different. So I dusted off my old Nikon D200 and put the lens on it, and seemed to focus the infinity OK. (at least as OK that manual focussing a digital camera gets) The digital confirmation light lit up, so I took a few shots and put them on the computer and everything looked in focus. I upped the ISO so that I could use a high enough shutter speed for the lens to be set wide open. (5.6 @ 500th sec.) Took a couple of shots at an object about 100 to 150 ft. away at both 100mm and 200mm, and it looked sharp at infinity. Now I'll admit that the difference between a FTN and a D200 is fairly large, but I can't believe the lens mount and film plane/sensor plane is different, or you wouldn't be able to use any Nikon film lenses on the digital cameras. Maybe I'm wrong, and this is some more digital voodoo stuff. Any thoughts on this?

rjbuzzclick · Apr 14, 2013

Here's a chart of camera mounts and register difference:

http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

It doesn't have a Nikon Digital flange distance, but does have a Nikon F flange distance of 46.5mm. The Petri flange distance is listed as 45.5mm. I would say that if it works for you, consider is good and just use it!

t-mount adapter question

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