I just spend some time using the auto fine tune on my D850 on various lenses and did some observations, some mentioned earlier and some just plain obvious in hindsight.
Tripod setup must be quite stable, since the whole procedure involves touching buttons unless someone can figure out how to do it remotely
Good AF taget and parallel to the sensor
Sensible distance from camera to target
It's an amazing tool for determining lens performance and consistency, any wear on zoom and/or focus cams show up immediately
Just for reference here ar some numbers
24-70 AFS 2.8 VR E best compromise is a 0
50mm AF-D 1.4 Japan also 0
180mm AF-D 2.8 Latest -10
60mm AFS 2.8 not sharp wide open at any distance
Comparison sharpness test revealed 55mm f/2.8 and 105mm Ais f/4 Micro to be amazing on D850 outstanding even wide open,,,
I was then testing a 70-200mm AFS VR II 2.8 Not my own and it was -18 at 200mm and down below 105mm then suddenly +10 at 70mm good luck shooting with that
Most amazing was to see how well the ancient AF-D lenses was focusing in live view, and after calibration how the D850 was able in AF-C to just nail focus pin point sharp every time hand held and that at an impressive speed, the 50mm AF-D 1.4 Japan super fast similar to 24-70 AFS 2.8 VR E and the 180mm AF-D 2.8 where also really really fast, my conclusion is that the auto focus system in the D850 really has a benefit on the AF-D lenses, so much that I reconsidered and bought a new 105mm AF-D 2 DC instead of the 105mm AFS f/1.4
Usually I study the AF target black and white transitions to evaluate sharpness, resolution and contrast - With the D50 and the above lenses especially the old Ais Micro-Nikkors - I was studing the surface texture of the AF target, even at several meters, quite impressive in my book.