Casio EX-Z450 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Ricoh CX2 has a 9.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Smooth Imaging Engine IV processor.
Below you can see the EX-Z450 and CX2 sensor size comparison.
Casio EX-Z450 and Ricoh CX2 have 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 CX2 has 33% larger pixel area (3.13µm2 vs 2.34µm2) compared to Casio EX-Z450, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.