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 L830 has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor .
Below you can see the SX30 IS and L830 sensor size comparison.
Canon SX30 IS and Nikon L830 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 SX30 IS has 14% larger pixel area compared to Nikon L830, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.