FujiFilm S2800HD has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Canon 550D has a
18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Digic 4 processor.
Below you can see the S2800HD and 550D sensor size comparison.
As seen above, Canon 550D has a 11.8x Larger sensor area than FujiFilm S2800HD. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.