The Nikon D850 monochrome is a Nikon D850 with its color filter array (CFA) removed by maxmax.com. NEF files 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.
I had posted most black and white images with the Nikon D850 monochrome in my review of the Nikon D850 monochrome in digloyd Advanced DSLR. I’ve now ported over various images to Zeiss Milvus and Zeiss Otus Lenses in diglloyd Zeiss DSLR Lenses:
Images up to full camera resolution, plus some frames at up to 183 megapixels upscaled using Gigapixel AI.