OM System OM-1 II has a
20.0MP Four Thirds (17.4 x 13 mm ) sized Stacked BSI Live MOS Sensor sensor . On the other hand, Pentax 645Z has a
51.0MP Medium format (44 x 33 mm ) sized CMOS sensor and features PRIME III processor.
Pentax 645Z's sensor provides 31MP more than OM System OM-1 II'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 645Z and OM System OM-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 OM-1 Mark II and 645Z sensor size comparison.
Sensor Size and Resolution Comparison image of OM System OM-1 II and Pentax 645Z Cameras
As seen above, Pentax 645Z has a 6.4x Larger sensor area than OM System OM-1 II. 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
OM System OM-1 II
or the
Pentax 645Z ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds versus Medium format),
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.
