Olympus E-M1 II has a
20.0MP Four Thirds (17.4 x 13 mm ) sized CMOS sensor and features TruePic VIII processor. On the other hand, Sony A77 II has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Bionz X processor.
Another difference between these two cameras is that Olympus E-M1 II's sensor lacks 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-M1 II and A77 II sensor size comparison.
As seen above, Sony A77 II has a 1.6x Larger sensor area than Olympus E-M1 II. 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-M1 II and Sony A77 II sensors have been tested by DxO and the results show that A77 II has a better overall score of 82, 2 points higher compared to E-M1 II's score of 80.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Olympus E-M1 II |
80 |
23.7 bits |
12.8 Evs |
1312 ISO |
Sony A77 II |
82 |
24.4 bits |
13.4 Evs |
1013 ISO |