Just one parenthetical note. Because Leica M lenses have manual aperture rings one will always achieve best focus by doing so with the lens wide open. If you try and focus with the lens stopped down to shooting aperture, particularly at smaller apertures, depth of field can lead to some inaccuracy. My method of working is to open the lens wide (counter-clockwise), focus, and then stop down to shooting aperture. Once you know how many "clicks" it is to a given aperture one can do this with the camera at eye level.