Both Pentax K20D and Samsung GX-20 have APS-C sized 15.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the K20D and GX-20 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K20D and Samsung GX-20 Cameras
Pentax K20D and Samsung GX-20 have the same sensor sizes so they will provide same level of control over the depth of field when used with 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 K20D and Samsung GX-20 sensors have been tested by DxO and the results show that GX-20 has a better overall score of 68, 3 points higher compared to K20D's score of 65.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K20D
65
22.9 bits
11.1 Evs
639 ISO
Samsung GX-20
68
23.1 bits
11.2 Evs
714 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 K20D
or the
Samsung GX-20 ,
including hyperfocal distance.
