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From my limited experience with my new Pentax K-3 iii monochrome camera I can say:
1. The same lens (Zeiss ZF 25mm f/2.8 at f/8) on the 25mp Pentax monochrome produces images that are much sharper than those I get from that same lens on my 42mp Z7 body. Same sensation I had when I first went from shooting regular digital images to shooting pixel shift images on the same digital camera. The difference was obvious and powerful.
2. I've made many digital black and white images from files captured by my color digital cameras. The middle grays and tones are clearly better from a true monochrome sensor.
3. Those of you who have not actually used a monochrome digital camera may not understand the significant increase in image quality a monochrome sensor camera provides over B&W images captured by a color digital camera. Try it, you will not believe the difference.
If you want to find out more about the affordable Pentax monochrome camera, check out this group -
https://www.pentaxforums.com/forums/219-pentax-k-3-iii-monochrome/