This GXR Mount A12 For Leica M Mount Lens is a "camera unit" for the GXR camera which accepts Leica M mount lenses. The GXR camera has an unusual design which incorporates a "body" combined with an interchangeable "camera unit". Each camera unit contains an image sensor and an image processing engine (most also include a lens). This camera unit has an APS-C size CMOS sensor and a focal plane shutter, but no lens. It will accept a Leica M mount lens and may be adapted to accept other lenses, as well. Various correction functions, such as color correcting at the corners, peripheral illumination, and distortion correction, are built-in.