FujiFilm S2800HD has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Ricoh PX has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Smooth Imaging Engine IV processor.
Below you can see the S2800HD and PX sensor size comparison.
FujiFilm S2800HD and Ricoh PX 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 S2800HD has 3% larger pixel area compared to Ricoh PX, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.