Ricoh G900 has a
20.0MP (1/2. ) sized BSI-CMOS sensor . On the other hand, Canon SX170 IS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the G900 and SX170 IS sensor size comparison.
As seen above, Canon SX170 IS has a infx Larger sensor area than Ricoh G900. 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.