Olympus E-500 has a
8.0MP Four Thirds (17.3 x 13 mm ) sized CCD sensor . On the other hand, Pentax KP has a
24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features PRIME IV processor.
Pentax KP's sensor provides 16MP more than Olympus E-500's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the E-500 and KP sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-500 and Pentax KP Cameras
As seen above, Pentax KP has a 1.6x Larger sensor area than Olympus E-500. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in 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 E-500
or the
Pentax KP ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds versus APS-C),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.