Pentax K-S1 has a
20.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Prime MII processor. On the other hand, Nikon D5100 has a
16.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features Expeed 2 processor.
Another difference between these two cameras is that Pentax K-S1'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-S1 and D5100 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K-S1 and Nikon D5100 Cameras
Pentax K-S1 and Nikon D5100 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. Pentax K-S1 and Nikon D5100 sensors have been tested by DxO and the results show that D5100 has a better overall score of 80, 2 points higher compared to K-S1's score of 78.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K-S1
78
23.5 bits
13.0 Evs
1061 ISO
Nikon D5100
80
23.5 bits
13.6 Evs
1183 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
Pentax K-S1
or the
Nikon D5100 ,
including hyperfocal distance.
