Both Canon G5 X and Olympus E-M1 II have 20.0 MP resolution sensors but Canon G5 X's sensor is 1″ (13.2 x 8.8 mm ) and Olympus E-M1 II's sensor is Four Thirds (17.4 x 13 mm ).
Since Olympus E-M1 II'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 Canon G5 X.
One other difference between these two cameras that is worth mentioning is that Olympus E-M1 II'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 G5 X and E-M1 II sensor size comparison.
As seen above, Olympus E-M1 II has a 1.9x Larger sensor area than Canon G5 X. 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. Canon G5 X and Olympus E-M1 II sensors have been tested by DxO and the results show that E-M1 II has a better overall score of 80, 18 points higher compared to G5 X's score of 62.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Canon G5 X |
62 |
21.4 bits |
12.3 Evs |
471 ISO |
Olympus E-M1 II |
80 |
23.7 bits |
12.8 Evs |
1312 ISO |