Canon S120 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized BSI-CMOS sensor and features Digic 6 processor. On the other hand, Olympus SP-570 UZ has a 10.0MP 1/2.3" (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the S120 and SP-570 UZ sensor size comparison.
As seen above, Canon S120 has a 1.5x Larger sensor area than Olympus SP-570 UZ. 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.
DxOMark Sensor Scores
Both Canon S120 and Olympus SP-570 UZ sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, S120 has scored 56, 28 points higher than SP-570 UZ.