Minolta SR mount

Minolta SR mount describes all Minolta 35mm SLR camera bodies with a bayonet mount for interchangeable manual focusing lenses, and all lenses designed to attach directly to these. All lenses for these bayonets built after 1961 are interchangeable between older and newer Minolta MF-SLR bodies (the lenses before 1961 feature a slightly different aperture leverage, and thus the automatic diaphragm may not work correctly). Three major stages have to be distinguished:

1. 1958-1966: Plain SR-bayonet featuring automatic diaphragm. Lenses are labelled Rokkor (pre-set) or Auto Rokkor (automatic diaphragm)
2. 1966-1977: Meter coupling added (often called MC bayonet) allowing full-aperture TTL measurement. Lenses are labelled MC Rokkor.
3. 1977-1998: MD lever added, which allows the reading of the smallest available aperture, often referred to as MD bayonet. Lenses are labelled MD or MD Rokkor (or MD Rokkor-X in North American markets.)
4. 1983-1998: X-600 mount reporting the lens maximum aperture design from the lens to the camera body which then engaged different sensitivity auto focus confirmation sensors in the camera body.

The SR models from 1958 to 1967 featured the initial design implementation of the SR bayonet. These were simple mechanical cameras without TTL metering or automatic exposure. The SR-7 was the only one with a built-in CdS meter, mounted on the side of the camera body and thus had the same metering capabilities as the external clip-on meters available for SR-1 and SR-3.

The introduction of the SR-T 101 in 1966 featured a meter coupling between pre-set aperture on lens and camera body. The camera had two CdS cells in the prism and metered the exposure through the lens (TTL). The later X-1 and XE models added an aperture-priority automatic exposure mode.

In 1977, the XD series introduced an additional tab on the lens which reported the smallest available aperture (f/16, f/22, or f/32 only) of an MD lens to a corresponding tab/switch on the camera body used by the camera electronics for an automatic calculation of approparite automatic diaphragm selection during exposure. That enabled the S (shutter priority automatic exposure) mode on XD models and the P (programmed automatic exposure) mode on the X-700.

On the 1983 Minolta X-600 camera, intended for Japanese-only distribution, there is also a focus assist and confirmation feature. The Minolta X-600 sensors need a clue from the lens as to the lens's maximum aperture so that the camera body can use it's appropriate range of light sensitivities from which to asses subject contrast for judging focus accuracy. There is a tang inside the lens that identifies either

• f/2.8 or larger maximum lens aperture, or
• f/3.5 or smaller maximum aperture.
  

The lens tang operates a switch inside the body of the X-600. There is no MD Auto Exposure feature on the X-600.

See also the Minolta SR mount category.

Links

• Evolution of the SR mount, all steps, at Minolta SLR Lenses [1]