Sony A850 has a Sony/Minolta Alpha lens mount and currently there are 143 native lenses available for this mount.
The latest released lenses that are compatible with the A850 are the Lensbaby Sol 45 DSLR, the Venus 105mm F2 and the Lensbaby Burnside 35.
A850 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on the A850.
Since Sony A850 has a Full frame sensor, it has a focal length multiplier of so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on A850.
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Sony A850 Lenses with Image Stabilization
Sony A850 Lenses with Weather Sealings