Olympus 1s has a
12.0MP 1/1.7' (7.44 x 5.58 mm ) sized BSI-CMOS sensor . On the other hand, Olympus SP-820UZ has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor .
Below you can see the 1s and SP-820UZ sensor size comparison.
As seen above, Olympus 1s has a 1.5x Larger sensor area than Olympus SP-820UZ. 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.