Both Pentax K20D and Pentax K-7 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 K-7 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K20D and Pentax K-7 Cameras
Pentax K20D and Pentax K-7 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
Both Pentax K20D and Pentax K-7 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, K20D has scored 65, 4 points higher than K-7.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Pentax K20D
65
22.9 bits
11.1 Evs
639 ISO
Pentax K-7
61
22.6 bits
10.6 Evs
536 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
Pentax K-7 ,
including hyperfocal distance.
