Leica S2 has a
38.0MP Medium format (45 x 30 mm ) sized CCD 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 13MP more than Leica S2'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.
One other difference between these two cameras that is worth mentioning is that Pentax 645Z's sensor doesn't have an 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 S2 and 645Z sensor size comparison.
Sensor Size and Resolution Comparison image of Leica S2 and Pentax 645Z Cameras
Leica S2 and Pentax 645Z 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.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Leica S2 and Pentax 645Z sensors have been tested by DxO and the results show that 645Z has a better overall score of 101, 25 points higher compared to S2's score of 76.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Leica S2
76
23.9 bits
12.2 Evs
824 ISO
Pentax 645Z
101
26.0 bits
14.7 Evs
4505 ISO
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
Leica S2
or the
Pentax 645Z ,
including hyperfocal distance.
