Casio EX-Z450 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Canon A800 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features DIGIC 3 processor.
Below you can see the EX-Z450 and A800 sensor size comparison.
Casio EX-Z450 and Canon A800 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.