FROM: Michael Quack SUBJECT: T4-Mount (War: Re: T2-Adapter passt nicht an Wundertuete ?) DATE: Tue, 03 Apr 2001 20:11:37 +0200 ORGANIZATION: The Q Continuum NEWSGROUPS: de.rec.fotografie Klaus Henkel wrote: > > Aber anscheinend niemand kann mir erklären, > was ein T4 eigentlich ist. Na aber sischer dat.... Robert Monaghan schreibt auf http://www.smu.edu/~rmonagha/third/mounts.html und an anderen Stellen in Auszügen: Tamron's president, Takeyuki Arai, invented the T-mount in 1959 (see Tamron's cult classic interchangeable mounts). You can find several versions of T-mounts, a solid fixed version and a later T2 version with three screws. The later T2 version is handy if you need to loosen the screws to let you rotate the inner ring of the T-mount adapter so the lens' aperture scales and controls face upwards. The later T-2 mount was also a 42mm x 0.75mm pitch purely mechanical mount (no auto-diaphragm action coupling). So far as I know, the T-3 mount was never marketed directly under that name, and may have remained an internal Tamron project leading to the T-4 and T-5 auto-diaphragm coupled lens mounts. T-mount lenses are available in a wide variety of focal lengths from a 7.5mm fisheye (Accura) to 640mm super-telephotos. Many mirror telephoto lenses have a T-mount adapter, since their apertures are fixed. Likewise, microscopes and telescopes are also commonly used with a T-mount style adapter system. You will also find accessories such as slide duplicators, extension tubes, and bellows which use the T-mount system. Most 35mm photographers are familiar with Tamron brand lenses, produced by Tamron Co. Ltd. (Taisei) of Japan. Tamron is the "T" in T-mounts, in T-2 mounts, in T-4 and even Vivitar's TX mounts. Tamron pioneered the concept of a third party lens maker providing optics in an interchangeable mount. Today, many of their lenses feature the adaptall and adaptall-2 automatic diaphragm mounts (an upgrade of the earlier adaptamatic system). The T-mount system was a development out of the highly popular M42 or Universal screw-thread mount design (often called the Pentax screw-mount after its best known popularizer). The M42 mount used a metric thread lens mount consisting of a simple lens thread 42mm in diameter, with a pitch of 1mm. The T-mount and associated T-2 mount also used a 42mm diameter, but a different thread pitch (0.75mm). The key difference in T-mount lenses was in their design. The lenses were designed to mount 55mm from the camera's film plane. This distance was significantly more than all the common camera brands such as M42 (45.46mm), Nikon (46.50mm), and Canon (42mm). (see W.J.Markerink's Table). While this screw-thread mounting wasn't bad when compared to simple M42 Universal screw thread cameras, it became limiting with the development of automatic diaphragm camera operation. Tamron responded by developing a T-4 system of automatic diaphragm operation (the intermediate T-3 mount was not mass-produced). In concert with Vivitar (one of their major importers), Tamron developed their TX version of this mount. This system does provide interchangeable mounts which preserve auto-diaphragm operation along with a manual operation setting for the older cameras. The next step in interchangeable mount evolution was the adaptamatic Tamron mount, which was popularized in the 1969-71+ timeframe. These earlier mounts had some teething problems, which were resolved in the later adaptall and adaptall-2 series mounts. T4-Adapter sind also satte 30 Jahre alt. Hat jemand Bock, das hier für die FAQ zu übersetzen und etwas zu straffen? Meine Zeit reicht dafür leider momentan nicht. -- Michael Quack http://www.photoquack.de What is the difference between erotic and kinky? Erotic is using a feather . . . kinky is using the whole chicken.