FujiFilm Finepix Z90 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Casio EX-ZR15 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Exilim Engine 5.0 processor.
Below you can see the Finepix Z90 and EX-ZR15 sensor size comparison.
FujiFilm Finepix Z90 and Casio EX-ZR15 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 FujiFilm Finepix Z90 has 14% larger pixel area compared to Casio EX-ZR15, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.