Ricoh GXR A12 50mm has a lens mount and currently there are 0 native lenses available for this mount.
The latest released lenses that are compatible with the GXR A12 50mm F2.5 Macro are the Nikon Micro-60mm f2.8D, the Carl Zeiss Makro-Planar T2/50 and the Carl Zeiss Makro-Planar T2/50.
Ricoh GXR A12 50mm doesn't have a sensor based image stabilization system but
481 of these lenses already comes with optical image stabilization.
Since Ricoh GXR A12 50mm has a APS-C 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 GXR A12 50mm F2.5 Macro.
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Ricoh GXR A12 50mm Lenses with Image Stabilization
Ricoh GXR A12 50mm Lenses with Weather Sealings