Both Olympus E-M5 and Panasonic GX85 have Four Thirds sized 16.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Panasonic GX85'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-M5 and GX85 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-M5 and Panasonic GX85 Cameras
Olympus E-M5 and Panasonic GX85 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
At Camera Decision, we also look at Dxo Mark sensors when available as we think it is a good indicator of image quality.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Olympus E-M5
71
22.8 bits
12.3 Evs
826 ISO
Panasonic GX85
71
22.9 bits
12.6 Evs
662 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-M5
or the
Panasonic GX85 ,
including hyperfocal distance.
