Leica S2 has a
38.0MP Medium format (45 x 30 mm ) sized CCD sensor . On the other hand, Pentax 645D has a
40.0MP Medium format (44 x 33 mm ) sized CCD sensor and features Prime II processor.
One other difference between these two cameras that is worth mentioning is that Pentax 645D'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 645D sensor size comparison.
Sensor Size and Resolution Comparison image of Leica S2 and Pentax 645D Cameras
Leica S2 and Pentax 645D 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 645D sensors have been tested by DxO and the results show that 645D has a better overall score of 82, 6 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 645D
82
24.6 bits
12.6 Evs
1262 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 645D ,
including hyperfocal distance.
