Olympus SZ-30MR has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features TruePic III+ processor. On the other hand, Canon D20 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Digic 4 processor.
Below you can see the SZ-30MR and D20 sensor size comparison.
Olympus SZ-30MR and Canon D20 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 Canon D20 has 32% larger pixel area (2.34µm2 vs 1.76µm2) compared to Olympus SZ-30MR, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.