Pekka Buttler, May 2025.
Basic Information on the T/T2 mount:
First off, it seems like the mount that is sometimes referred to as the T-mount and the lens mount that is referred to as the T2 mount are one and the same. I would speculate that the T-mount (T stands for Taisei Kogaku, nowadays known as Tamron) was renamed the T2 mount to lessen the risk of mistaken identity. Read on for more details.
Second, the T and T2 mounts are not – strictly speaking – lens mounts as there has never been a camera that uses these mounts, but is instead an intermediate mount. The purpose of such mounts is to allow third party lens manufacturers to easily make their lenses usable on a wide range of camera bodies, simply by attaching a suitable adapter to the lens.
T/T2 mount specifications and identification
Mount type: Thread mount (M42x0,75)
Flange focal distance: 55 mm
Sensor Size: 36,0 mm x 24,0 mm (Full frame)
Mount communication: none
Characteristics of a T/T2 mount:
[1] 42 mm diameter threads with a thread pitch of 0,75 mm (M42×0.75)
(no camera–lens communication)
The T/T2 intermediate mount.
In 1957 Tamron had started to manufacture camera lenses with the intention of these lenses being used on a wide range of cameras, using a thread-mounted intermediate mount, named simply the T-mount, later referred to as the T2 mount. This approach showed all third-party lens manufacturers the potential advantages of using intermediate mounts.
However, the problem with the T/T2 mount (as well as many other early interchangeable mounts such as the M47 mount) was that it did not in any way facilitate camera-lens communication. In the age of manual and preset apertures that was enough, but as auto aperture started becoming the norm, Tamron had to develop a new intermediate mount (the Tamron Adapt-a-matic mount).
Even so, because of its exceedingly simplicity and generous flange focal distance, the T/T2 mount did not disappear. Instead, it was adopted by some other third party manufacturers and remained an important factor in b third party lens manufacture, mostly for budget tele lenses, especially catadioptric (mirror) lenses. The T/T2 mount also plays a role in mating telescopes to cameras.
Adapting T/T2 lenses
If you intend to adapt your T/T2 Adaptall lens to a SLR…
There are T/T2 adapters practically all SLR systems available. These adapters allow you to use the T/T2 lens as a manual focus manual aperture lens.
If you intend to adapt your Tamron Adaptall lens to a mirrorless camera
There are basically two ways. If your T/T2 lens came with an adapter attached (such as the Minolta SR mount), you can consider keeping that adapter on the T/T2 lens and getting an adapter from (e.g. Minolta SR) to your mirrorless system (you might already have such an adapter).
Alternatively, you can procure a T2->your mirrorless mount adapter. This has the advantage of using only one adapter (less play), but is less modular.