FujiFilm F300EXR has a
12.0MP 1/2-inch (6.4 x 4.8 mm ) sized CCD sensor and features EXR processor. On the other hand, Fujifilm F550 EXR has a
16.0MP 1/2-inch (6.4 x 4.8 mm ) sized EXRCMOS sensor and features EXR processor.
Below you can see the F300EXR and F550 EXR sensor size comparison.
FujiFilm F300EXR and Fujifilm F550 EXR 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 F300EXR has 32% larger pixel area compared to Fujifilm F550 EXR, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.