The new monochrome mode in Sigma Photo Pro seems to produce just about flawless black and white images from the Sigma DP Merrill. Three retina-grade examples now posted in my review of the Sigma DP Merrill cameras.
Please note that while these example conversions were done with Sigma’s Sigma Photo Pro software, Iridient Developer offers a special “XDR Monochrome” mode for very high quality conversions to black and white, with claimed improvements in noise, dynamic range and fine detail rendition.
Side note: more flexible (true RGB sensor), autofocus, better easy of use, and 1/10 the cost of the Leica M Monochrom. Of course the Leica MM is full frame and will do much better at high ISO, but I see no reason to complain about the DP Merrill monochrome ability