Pentax K-1 II has a
36.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features PRIME IV processor. On the other hand, Pentax K-3 III Mono has a
26.0MP APS-C (23 x 15.5 mm ) sized BSI-CMOS sensor and features PRIME V processor.
Pentax K-1 II's sensor provides 10MP more than Pentax K-3 III Mono'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 similarity between these two cameras is that both Pentax K-3 III Mono and Pentax K-1 II 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 K-1 Mark II and K-3 III Monochrome sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-1 II and Pentax K-3 III Mono Cameras
As seen above, Pentax K-1 II has a 2.4x Larger sensor area than Pentax K-3 III Mono. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in 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-1 II
or the
Pentax K-3 III Mono ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Full frame versus APS-C),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.
