Olympus E-PM1 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features TruePic VI processor. On the other hand, Panasonic GX850 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine processor.
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-PM1 and GX850 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-PM1 and Panasonic GX850 Cameras
Olympus E-PM1 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. On the other hand, since Olympus E-PM1 has 29% larger pixel area compared to Panasonic GX850, 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-PM1 and Panasonic GX850 sensors have been tested by DxO and the results show that GX850 has a better overall score of 73, 21 points higher compared to E-PM1's score of 52.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Olympus E-PM1
52
21.0 bits
10.3 Evs
499 ISO
Panasonic GX850
73
23.2 bits
13.3 Evs
586 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-PM1
or the
Panasonic GX850 ,
including hyperfocal distance.
