I am able to fit my Carl Zeiss Contax Rangefinder lens Biogon 21mm f4.5 on my Sony A7R body using two adapters, namely Contax (outside mount) to Leica M adapter and Leica M to Sony E Mount adapter. My Sony Leica M Mount adapter has a helicoid component; hence It becomes the focussing unit for my Zeiss lens (designed originally to use the built-in focussing component of the Contax Rangefinder camera body). However, at 'infinity' setting with the two adapters, it is slightly unsharp. I feel tha the two adapters are correctly specified and made and that the unsharpness lies with the lens. I wonder whether my lens has been collimated accurately. Any comment about my difficulty would be appreciated.