Olympus E-510 has a
10.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Olympus E-PM2 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor .
Olympus E-PM2's sensor provides 6MP more than Olympus E-510's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the E-510 and E-PM2 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-510 and Olympus E-PM2 Cameras
Olympus E-510 and Olympus E-PM2 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. On the other hand, since Olympus E-510 has 59% larger pixel area compared to Olympus E-PM2, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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-510 and Olympus E-PM2 sensors have been tested by DxO and the results show that E-PM2 has a better overall score of 72, 20 points higher compared to E-510's score of 52.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Olympus E-510
52
21.2 bits
10.0 Evs
442 ISO
Olympus E-PM2
72
22.7 bits
12.2 Evs
932 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
Olympus E-510
or the
Olympus E-PM2 ,
including hyperfocal distance.