graybeard

OK, I said I was going to break the record for dumb questions, and if you didn't believe me than try this: What is a T-mount? I see this term frequently, but it always seems to be in different contexts, so I can't quite piece it together. To my thinking, there is a camera body mount, a lens mount, and if not the same an adapter. So what is a T-mount? So go ahead and snicker, but digital has created a whole new vocabulary, and I still have a 35mm brain. Also please, for future reference, please do not include geometry, ohm's law, or other exotica in your explanations. Thanks.

MadMikeOne Loc: So. NJ Shore - a bit west of Atlantic City

Heck, I googled for "t-mount" and found confusion. Hopefully, you will get some responses that make sense. Now you have me wondering what this is .

lightcatcher Loc: Farmington, NM (4 corners)

Canon telescope mount.

tsilva Loc: Arizona

The t-mount has been around since 1957. I doubt if there was much digital going on so your 35mm brain will work just fine.

T-mount
Watch this page
T-mount
Type screw
External diameter 42 mm
Flange 55 mm
Connectors None
The T-mount is a standard lens mount for cameras and other optical assemblies. The usual T-mount is a screw mount using a male 42×0.75 (42 mm diameter, 0.75 mm thread pitch) metric thread on the lens with a flange focal distance of 55 mm and a mating female 42mm thread on a camera adapter or other optical component. This thread form is referred to as T-thread. (This should not be confused with the M42 lens mount which is also 42 mm diameter, but has a 1 mm thread pitch.)

The "T" is said to stand for Tamron or Taisei, a Japanese manufacturer that released in 1957 the first of a line of aftermarket camera lenses that fit 35 mm SLR cameras built by various manufacturers using their universal T-mount. On the first model, the mini T-mount used a M37×0.75 thread; Tamron’s canonical M42×0.75 T-thread didn’t appear on the market until about 1962. The company referred to it variously as a T-mount, T-thread, T-adapter, or a T-400, but not as a T-2,which is simply the name that Soligor used for its version of the T-adapter. The proprietary lens mount of each camera manufacturer was adapted to the T-mount thread with a simple adapter. Thus a retailer could stock a small number of expensive lenses that would fit a large number of camera brands using a selection of inexpensive adapters.

Some T-mount lenses accept a T-adapter that lacks its threaded inner ring,and simply slides onto the T-mount lens. It is secured only by 3 set screws that match a channel on the lens barrel, such that the barrel is not deformed by the set screws and the adapter can therefore be removed with no damage.

As a common mechanical interface, the T-mount allows components of various manufacturers to be interchanged and assembled. The T-mount is a solely mechanical specification. Electrical or mechanical connections (such as for autofocus) are generally not provided, although Sigma’s YS Mount featured an automatic diaphragm coupling.

Besides cameras, T-mounts are used in optical breadboard prototyping components as well as telescope and microscope attachments. The T-mount is also a standard way to mount a camera to a microscope to photograph pathological specimen slides or to a 1.25″ telescope eyepiece.

AdaptersEdit

Because the T-mount lenses have a long flange distance of 55 mm and most 35 mm cameras have shorter flange distances, a simple mechanical adapter called T-Ring is needed to adapt a T-mount lens to any camera body without optical correction to achieve infinity focus.

An adapter ring has a female M42×0.75 metric thread on one side and a corresponding lens mount of the camera body on the other side. A T-adapter consists of an inner ring with T-mount thread and an external ring with corresponding lens mount. The T-ring and the T-2 ring are identical to each other. Both of them have the inner and outer ring. The two rings (inner and outer) are held together by 3 peripheral screws on the external ring. Loosening these screws allows rotation between the lens and the camera body. This is especially useful when the camera body is attached to telescopes or microscopes.

Standard T-rings usually have the same external diameter of their inner ring because some T-mount lenses have their inner ring built onto the flange, thus the external ring of the T-adapter can be directly attached, as described above.

The thickness of the external ring on an adapter is equal to the difference of the flange distance between the T-mount and the corresponding lens mount in order to achieve infinity focus. Other large format camera lenses have a flange distance longer than 55 mm. They can be attached to smaller format cameras with a combination of corresponding lens-to-T-mount-adapter and a T-Ring.

See alsoEdit

Tamron
M42 lens mount
C mount
K mount
ISO metric screw thread
External linksEdit

Making Digital Camera Microscope Adapters. Various examples and machining details of custom-made T-mount adapters.
Read in another language

BHC Loc: Strawberry Valley, JF, USA

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A T-mount is best described as an interchangeable interface system. Originally inexpensive lens makers made their lenses in T-mounts; T-mount adapters could be purchased for just about any body, so you could match the lens to the camera. Eventually, telescope manufacturers realized that this was the ideal was to adapt cameras to "astro-scopes". I have a T-mount on my small Meade telescope and it takes everything from my Nikon EM (when my grandson lets me "borrow" it) to my FM2n and D3200. Of course everything is manual (sometimes I have to use stop down metering) but it a simple solution to a complex problem. I also purchased a T-mount for my Panasonic μ4/3. One big advantage of the T-mount is that the mount spins freely within the ring allowing correct alignment to any lens; three screws on the ring then secure the mount (and thus the camera) in alignment. The T-mount is left attached to the lens. For (generally) less than $30 per scope you can adapt your best body to most astronomical scopes. You can occasionally find some excellent lenses that will mount on your camera. If you don't mind doing everything manually, you can even use a T-mount to match your top end Canon body to a Nikon bellows and micro lens for super macro photography.

When I started in SLR photography, many considered T-mounts to be a cheap way to get long glass on a standard body. It was "poor mans solution" to a common problem and many "real" photographers considered it a gimmick. Oh if I only knew then what I know now......

MadMikeOne Loc: So. NJ Shore - a bit west of Atlantic City

Mogul, thanks for your explanation. It makes sense and I can visualize the set-up.
Tsilva's response is what I found when I googled "t-mount". Made absolutely NO sense!
Thanks again!

graybeard

OK got a better idea now..... that wiki paste job is kind of incoherent,,,,, it was one of the things that confused me.... and btw Mogul, shouldn't your pic be of a 2-6-0 not a 4-4-0?

BHC Loc: Strawberry Valley, JF, USA

Good Catch! Actually I've a 4-4-0, a 4-2-0T, an 0-6-0T, a 4-8-8-2, a 4-6-6-4 and a 4-8-8-4 in addition to a 2-6-0. My most common avatar though is the 0-6-0T Granite Rock 10 from SSRR. It's nice to know that others remember Whyte designations. 8-) 8-) 8-)

graybeard

Well Ive got a 4-6-6-4, 2-8-8-2, 2-10-2, 2-10-0, 4-8-4 (x3),,,,, 4-4-4-4, 4-8-2 (x2), 4-8-0, 2-8-4 (x2), 2-8-2 (x2), 2-8-0 (x3),,,
4-6-4 (x3), 4-6-2 (x4), 4-6-0, 2-6-2, 2-6-0, 4-4-2 (x2),,,,,,,,,,, 4-4-0, 0-8-0 (x2), 0-6-0, 0-4-0, 0-6-0T, and 0-4-0T. Plus 22 diesels. on my layout in the attic.

RWR Loc: La Mesa, CA

Tsilva's response describes exactly what a T-mount is! How much clearer do you want it??

http://en.wikipedia.org/wiki/T-mount

BHC Loc: Strawberry Valley, JF, USA

You're quite right; Tsilva's explanation is much better than mine. The time line shows that he must have posted his while I was typing mine. If I had known that, I wouldn't have bothered.

BHC Loc: Strawberry Valley, JF, USA

That's quite a selection. How much rolling stock do you have in addition to your locomotives? Actually, I don't get to play with the toy trains; the owners and operators here are quite careful about who touches their delicate equipment. That's why most of my avatars are pictures of the real thing. We just got a ten-wheeler out of the shops, but it's usually positioned on a track that makes photography difficult. I'm hoping to catch it on the turntable one of these days. By the way, is your 0-6-0T a Liberty Engine?

graybeard

Tsilva's response was straight out of icky-wiki, that font of the inaccurate, incoherent, and incomprehensible. Encyclopedia Britanica goes pop, and so democratic that anybody can contribute whatever they want !

graybeard

Also, while there may be a specific definition for a T-mount, it is obvious from the way it is often used that there is also a generic or non-specific usage that makes its exact meaning unclear. T-ring is another term I hear. For my purpose, I needed to know how lens A could be mated to camera B. What EXACTLY it would take. Not a "oh it needs a T-mount". Anyway, thank you all for your responses. Yes, T-silva, I was alive and functioning in 1957, but I must have missed the news that day.

BHC Loc: Strawberry Valley, JF, USA

By golly, you're right! Oh, well, I know I must have slipped a few times and forgotten a proper reference and/or attribution. But for something that complicated, a "per http://en.m.wikipedia.org/wiki/T-mount" would have been helpful to allow future reference.