For all of you focus stackers out, the Macro Digitar is designed to be sharp wide open. Apparently Rodenstock's is meant to be stopped down to F/8...
Moving to 1:1 halves your aperture size, so if your lens is designed for use at F/8, then by the time you get to 1:1 your at F/16 which is in the diffraction zone for medium format digital. Use the macro digitar M wide open with a 40. 60. or 80 megapixel and you'll have the sharpest macro work of all.