Canon 7D has a
18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Dual Digic 4 processor. On the other hand, 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.
Below you can see the 7D and SX30 IS sensor size comparison.
As seen above, Canon 7D has a 11.8x 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.