Both Pentax 645Z and Fujifilm GFX 50S II have Medium format sized 51.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another difference between these two cameras is that Pentax 645Z's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the 645Z and GFX 50S II sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax 645Z and Fujifilm GFX 50S II Cameras
Pentax 645Z and Fujifilm GFX 50S II have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Pentax 645Z
or the
Fujifilm GFX 50S II ,
including hyperfocal distance.
