Olympus E-PM2 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Samsung Galaxy NX has a
20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features DRIMe IV processor.
Below you can see the E-PM2 and Galaxy NX sensor size comparison.
As seen above, Samsung Galaxy NX has a 1.6x Larger sensor area than Olympus E-PM2. 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.