Canon SX30 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor. On the other hand, Nikon D5100 has a
16.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features Expeed 2 processor.
Below you can see the SX30 IS and D5100 sensor size comparison.
As seen above, Nikon D5100 has a 13.2x Larger sensor area than Canon SX30 IS. 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.