Both Fujifilm X-T20 and Pentax K-3 have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another similarity between these two cameras is that both Pentax K-3 and Fujifilm X-T20 sensors lack anti-alias (Low-Pass) filters. 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 X-T20 and K-3 sensor size comparison.
Sensor Size and Resolution Comparison image of Fujifilm X-T20 and Pentax K-3 Cameras
Fujifilm X-T20 and Pentax K-3 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the 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
Fujifilm X-T20
or the
Pentax K-3 ,
including hyperfocal distance.
