T2 connection
The T2 connection is a common thread lens connection for cameras and other optical devices. In 1957 the Japanese lens manufacturer Tamron introduced an extensive series of interchangeable lenses for 35 mm cameras , all of which had a T2 connection. Even today, T2 is the de facto standard for connecting cameras to telescopes or microscopes .
Like the M42 connection, the T2 connection has an external thread diameter of 42 mm. However, the thread pitch is only 0.75 mm (height per revolution) in contrast to 1 mm for the M42. The back focus is set at 55 mm. The T2 standard is a purely mechanical specification . How electrical or other mechanical elements of the connection from lens to camera are to be implemented is not specified. The biggest disadvantage is the lack of aperture transfer from the lens to the camera - open aperture measurements and aperture - or automatic programs are not possible with T2 (but the use of the aperture priority is possible ).
With the original T connection, the external connection and the internal T thread are in one part, so they cannot be rotated against each other. T2 is a further development of the T-connection, in which the internal thread is located in a separate ring that can be rotated with respect to the outer ring and can be fixed in this - usually with clamping screws. This is to ensure that the orientation z. B. can be adjusted by lens adjustment marks so that the label faces the user.
Lenses with a T2 thread with a suitable lens adapter can also be used in digital camera systems with a correspondingly smaller flange focal length (which is the case for all common systems) . Such T2 adapter, sometimes called T-Ring, serve primarily to small picture - SLR various lenses to attach that have a T2 connection. T2 adapters are available for almost all common SLR cameras with interchangeable lenses. The external connection corresponds to the camera bayonet or thread.
In astrophotography , an extension tube with a T2 connection (42 mm) is often used for eyepiece projection , since eyepieces with a 1.25 ″ plug size then fit into the tube - without much lateral play. The digital camera is then mounted with a proprietary bayonet lock using a T adapter.
Web links
- Thread in the photo area , Thread-Normen.de