Both OM System OM-5 II and Samsung NX20 have 20.0 MP resolution sensors but OM System OM-5 II's sensor is Four Thirds (17.4 x 13 mm ) and Samsung NX20's sensor is APS-C (23.5 x 15.7 mm ).
Since Samsung NX20'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 OM System OM-5 II.
Below you can see the OM-5 Mark II and NX20 sensor size comparison.
Sensor Size and Resolution Comparison image of OM System OM-5 II and Samsung NX20 Cameras
As seen above, Samsung NX20 has a 1.6x Larger sensor area than OM System OM-5 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.
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
OM System OM-5 II
or the
Samsung NX20 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds versus APS-C),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.
