Olympus SP-590 UZ has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Olympus SP-620 UZ has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III+ processor.
Below you can see the SP-590 UZ and SP-620 UZ sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus SP-590 UZ and Olympus SP-620 UZ Cameras
Olympus SP-590 UZ and Olympus SP-620 UZ 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
Olympus SP-590 UZ
or the
Olympus SP-620 UZ ,
including hyperfocal distance.