I see David is now offering adapters for the 1.4x and 2x convertors (Nikon only I think) - that means that the lens can stay on R mount... http://www.leitax.com/conversion/leica/APO-Extender-R_1.4x/index.html http://www.leitax.com/conversion/leica/Apo-Extender-R_2xROM/index.html john