Both Pentax K-m and Sony A100 have 10.0 MP resolution sensors but Pentax K-m's sensor is APS-C (23.5 x 15.7 mm ) and Sony A100's sensor is APS-C (23.6 x 15.8 mm ).
Since Sony A100's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Pentax K-m.
Below you can see the K-m and A100 sensor size comparison.
Pentax K-m and Sony A100 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 K-m and Sony A100 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, K-m has scored 64, 3 points higher than A100.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Pentax K-m |
64 |
22.4 bits |
11.4 Evs |
513 ISO |
Sony A100 |
61 |
22.0 bits |
11.2 Evs |
476 ISO |