The Sony A Mount System is the older of the two Sony camera mount systems. Originally, this mount was used by Minolta, a Japanese manufacturer of analog (and digital) SLR Kameras. At Minolta, the A Bayonet was the successor of ST Bayonett (AR, MD, MC Mount), which introduced both autofocus and an later the electric aperture control.
Due to the fact that the Sony A Mount system is a 1 to 1 copy of the Minolta A mount syste,, all mor or less old Minolta autofocus lenses are compatible with Sony cameras. This also includes third party lenses such as Tamron, Sigma and Exakta. The only exception is the Minolta VECTIS system, which has its own mount system.
Apart from the lenses originally developed for Minolta, there are unfortunately not many possibilities to use lenses with adapters that do not need a compensating lens. The only possibilites I know are the adaptable M42 lenses. Next to the M42 adapters there are only adapters for T2 and some medium format camera lenses. (For example Pentacon SIX)
M42 lenses can be used by using a very thin adapter without sacrificing infinity focus or quality. There are only some lenses that cause a problem with the aperture. Some M42 lenses have a small “pin” that sticks out of the back side. Since this “pin” must be pressed in order to adjust the aperture, it is necessary to fix the pin tiwth a small piece of adhesive tape. Another possibility is to unmount the rear end of the lens and dismount the spring and the pin. I only recommend this variant to people who know the mechanics well and can handle a screwdriver and tiny screws.
Due to the Minolta connection, these lenses are the perfect choice. There is autofocus availiable and the connection between the camera and the lens is working. Among the special treasures are:
- Minolta AF 50mm f1.4
- Minolta AF 100mm f2
- Minolta AF Macro 100mm f2,8
- Tamron F Macro 90mm f2,8
Compability with M42 adapters and M42 lenses, offers a completely different world of lenses. In this case, you lose the autofocus and the communication between the camera and the lens, but you can use way cheaper and more charactaristical lenses. There are no limits to your creativity.
Corresponding lens reviews can be found here.