Casio EX-10 has a
12.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CMOS sensor and features Exilim Engine HS 3 processor. On the other hand, Canon S90 has a
10.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the EX-10 and S90 sensor size comparison.
Casio EX-10 and Canon S90 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 Canon S90 has 20% larger pixel area (4.16µm2 vs 3.46µm2) compared to Casio EX-10, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.