Casio EX-ZR800 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features EXILIM Engine HS 3 processor. On the other hand, Ricoh WG-20 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the EX-ZR800 and WG-20 sensor size comparison.
Casio EX-ZR800 and Ricoh WG-20 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Ricoh WG-20 has 15% larger pixel area (2.04µm2 vs 1.76µm2) compared to Casio EX-ZR800, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.