The Nikon D850 monochrome is a Nikon D850 with its color filter array (CFA) removed by maxmax.com. The NEF files are converted to monochrome DNG via LibRaw Monochrome2DNG and “Method B”, then processed using Adobe Camera Raw. Doing so avoids any demosaicing and thus retains full spatial resolution.
This page compares the Nikon D850 monochrome to an unmodified Nikon D850 using the Zeiss Milvus 35mm f/1.4, focusing on detail and textural rendition. I have another more involved comparison planned (with five filter variants), but that is too time consuming during my last few wonderful October days in the mountains.
Images at up to full resolution are included in both color and black and white. A black and white rendition from the unmodified (color) Nikon D850 is compared to the Nikon D850 monochrome image, including crops from each from 180 megapixel images. Also, full 180 megapixel upscaled images(2X linear enlargement) from Gigapixel AI are included for comparison.