Pentax K-3 II has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Prime III processor. On the other hand, Fujifilm S2 Pro has a
6.0MP APS-C (23 x 15.5 mm ) sized CCD sensor .
Pentax K-3 II's sensor provides 18MP more than Fujifilm S2 Pro's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Another difference between these two cameras is that Pentax K-3 II'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 K-3 II and S2 Pro sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-3 II and Fujifilm S2 Pro Cameras
Pentax K-3 II and Fujifilm S2 Pro 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
Pentax K-3 II
or the
Fujifilm S2 Pro ,
including hyperfocal distance.