Both Pentax K200D and Nikon D3000 have APS-C sized 10.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the K200D and D3000 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K200D and Nikon D3000 Cameras
Pentax K200D and Nikon D3000 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
Both Pentax K200D and Nikon D3000 sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, K200D has scored 64, 2 points higher than D3000.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K200D
64
22.4 bits
11.4 Evs
561 ISO
Nikon D3000
62
22.3 bits
11.1 Evs
563 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 K200D
or the
Nikon D3000 ,
including hyperfocal distance.
