Casio EX-Z800 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Exilim Engine 5.0 processor. On the other hand, Canon SD780 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the EX-Z800 and SD780 IS sensor size comparison.
Casio EX-Z800 and Canon SD780 IS 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.