Both Olympus E-PM2 and Pentax K-5 have 16.0 MP resolution sensors but Olympus E-PM2's sensor is Four Thirds (17.3 x 13 mm ) and Pentax K-5's sensor is APS-C (23.7 x 15.7 mm ).
Since Pentax K-5'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 Olympus E-PM2.
Below you can see the E-PM2 and K-5 sensor size comparison.
As seen above, Pentax K-5 has a 1.7x Larger sensor area than Olympus E-PM2. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in 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. Olympus E-PM2 and Pentax K-5 sensors have been tested by DxO and the results show that K-5 has a better overall score of 82, 10 points higher compared to E-PM2's score of 72.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Olympus E-PM2 |
72 |
22.7 bits |
12.2 Evs |
932 ISO |
Pentax K-5 |
82 |
23.7 bits |
14.1 Evs |
1162 ISO |