Both Olympus E-PM2 and Panasonic GX850 have 16.0 MP resolution sensors but Olympus E-PM2's sensor is Four Thirds (17.3 x 13 mm ) and Panasonic GX850's sensor is Four Thirds (17.3 x 13 mm ).
Since Panasonic GX850'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.
One other difference between these two cameras that is worth mentioning is that Panasonic GX850's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the E-PM2 and GX850 sensor size comparison.
Olympus E-PM2 and Panasonic GX850 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
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 Panasonic GX850 sensors have been tested by DxO and the results show that GX850 has a better overall score of 73, 1 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 |
Panasonic GX850 |
73 |
23.2 bits |
13.3 Evs |
586 ISO |