I could not resist trying out the D850 built-in focus stacking, which can be found in the Photo Shooting Menu. It works with AF lenses, it basically takes a picture, moves the focus a little farther away specified by a step size value, and repeats this for a number of shots specified. The time interval between shots can be specified, and the shots can be made in silent mode. Determining the proper step size to use is by trial and error, I have not seen a formulae for that yet.
After each finished sequence of shots focus stays at the position of the last shot; if the wanted depth is not reached one can easily repeat the sequence until it is.
I made one stack (20 shots, step size 2) with the 105VR full-open, effectively at f/3.2, and processed it in the test version of Zerene Stacker. Some stacking errors are visible, e.g. around the shoulders. It is my first stack, and probably also my last, this is not exactly my cup of tea. A 50% reduced .jpg is attached. I know, Jerommeke needs a shower