The T-mount is a standard

lens mount A lens mount is an interface – mechanical and often also electrical – between a photographic camera body and a lens. It is a feature of camera systems where the body allows interchangeable lenses, most usually the rangefinder camera, sin ...

for

camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with ...

s 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 For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus or register, depending on the usage and source ...

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 The M42 lens mount is a screw thread mounting standard for attaching lenses to 35 mm cameras, primarily single-lens reflex models. It is more accurately known as the M42 × 1 mm standard, which means that it is a metric screw thread of ...

which is also 42 mm diameter, but has a 1 mm thread pitch. The T-thread is sometimes described as "M42×0.75," which is the usual manner in which to describe a metric thread.) The "T" is said to stand for

Tamron is a Japanese company manufacturing photographic lenses, optical components and commercial/industrial-use optics. Tamron Headquarters is located in Saitama City in the Saitama Prefecture of Japan. The name of the company came from the surna ...

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 An autofocus (or AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system ...

) 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 A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...

and

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

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.

Adapters

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 its closest focus distance. An adapter ring has a female M42×0.75 metric thread on one side and a corresponding

of the

camera body A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

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. Since some DSLRs won't meter without electronic lens data, some adapters are now sold fitted with a

Dandelion chip A dandelion chip is an electronic device, installed on the bayonet mount of a non-electronic camera lens or adapter, which enables electronic interoperation with certain cameras. The device consists of an integrated circuit connected to a series of ...

which can be programmed to identify the focal length and aperture limits and enable metering and in some cases focal confirmation.Advertisement for T-mount with Dandelion chip
accessed 5 October 2015 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.

References

{{Reflist

External links

Making Digital Camera Microscope Adapters.
Various examples and machining details of custom-made T-mount adapters. Lens mounts Film and video technology

Adapters

See also

References

External links