Canon S120 has a
12.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized BSI-CMOS sensor and features Digic 6 processor. On the other hand, Olympus TG-310 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III+ processor.
Below you can see the S120 and TG-310 sensor size comparison.
As seen above, Canon S120 has a 1.5x Larger sensor area than Olympus TG-310. 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.