Nikon D850 converted to monochrome.
Comparisons using the same lens, same ISO, same aperture, tripod mount, timed shutter release. Shutter speeds different because the monochrome is more sensitive. Sample pictures are from JPG pictures shot in Fine mode dropped into Photoshop with no processing. Comparisons are crops at 100%. These pictures are screenshots of Photoshop that have been further compressed into JPG pictures - actual RAW quality is higher.
We can make this camera as a visible light monochrome camera or a full spectrum UV-VIS-IR camera with a fused silica (quartz) coverglass for extended UV response. Since the D850 is a Back Side Illuminated (BSI) sensor, the camera has extended UV response when compared to a typical front side illuminated sensor.
For optimal results from a monochrome camera, shoot in RAW and use a processor that understands that the camera sensor is monochrome debayered. One of the best processors current is Monochrome2DNG fro Iliah Borg who also wrote FastRawViewer.
Some free options are DarkTable and RawTherapee using the monochrome debayer option.
A Mac-only really good processor is Accuraw Monochrome
To see RAW NEF file showing resolution test chart from the monochrome and stock camera you can click on
One measurement of a optical system (Camera + Lens + Shooting Conditions) is the Modulation Transfer Function (MTF). The MTF measures how well the sytstem captures contrast in an image as a function of spatial frequency. Using the same lens, same aperture, same tripod, same lighting, etc, we measured the MTF of a stock D850 versus a monochrome D850 using 8-bit JPG. If we had used RAW, the difference would be greater. Amazingly, even at 8-bit JPG, the difference between the two cameras is startling.
Notice that the monochrome 850 is almost 2.75 Cycles/Pixels at 0.5 MF and is less then 2.0 Cycles/Pixel at 0.5 MF. That's almost a 50% difference!
Click on images to see at 100%