Kodak Z915 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Olympus E-P1 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features TruePic V processor.
Below you can see the Z915 and E-P1 sensor size comparison.
As seen above, Olympus E-P1 has a 8.0x Larger sensor area than Kodak Z915. 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.