Casio EX-Z450 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Nikon S100 has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Expeed C2 processor.
Below you can see the EX-Z450 and S100 sensor size comparison.
Casio EX-Z450 and Nikon S100 have 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 Casio EX-Z450 has 32% larger pixel area compared to Nikon S100, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.