Kodak Z981 has a
14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Casio EX-Z90 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the Z981 and EX-Z90 sensor size comparison.
Sensor Size and Resolution Comparison image of Kodak Z981 and Casio EX-Z90 Cameras
Kodak Z981 and Casio EX-Z90 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Kodak Z981
or the
Casio EX-Z90 ,
including hyperfocal distance.