The A12 28mm F2.5 is a lens unit that slides into Ricoh's GXR body. The GXR system takes a novel approach by offering interchangeable slide mount 'lens units' - sealed modules containing both optics and sensor, meaning it can switch from a large (APS-C) sensor with a fast prime lens to a tiny one (as in compact cameras) with zoom lenses. The Ricoh GXR/A12 28mm F2.5 Macro combines a 12MP APS-C sensor with a 28mm prime lens. The module offers a good image quality and together with the GXR body great build quality and handling. It is a compact alternative to a DSLR if 28mm is your focal length of choice and you can live with the sometimes a little sluggish contrast detect AF.