 Earlier 1, 2, or 3 cam lenses may be upgraded to ROM but this entails removal of both sloped cams, meaning that the lens will no longer be compatible with Leicaflex series cameras.The flange focal distance of 47 mm is fairly large, meaning that few other systems' lenses can be adapted to fit on a Leica R and retain infinity focus, but R lenses can be converted to other systems.The distance is only 0.5 mm larger than the Nikon F-mount, which is not sufficient to make a workable adapter, however, at least one Nikon camera has been modified with a Leica R bayonet mount to take R lenses, and at least two manufacturers make replacement mounts, allowing many Leica R lenses to be used directly on various camera systems, such as Nikon F mount cameras.