Sony A900 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 A900 are the Lensbaby Sol 45 DSLR, the Venus 105mm F2 and the Lensbaby Burnside 35.
A900 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on the A900.
Since Sony A900 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 A900.
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Sony A900 Lenses with Image Stabilization
Sony A900 Lenses with Weather Sealings