Canon D30 has a
3.0MP APS-C (22.7 x 15.1 mm ) sized CMOS sensor . On the other hand, Nikon D100 has a
6.0MP APS-C (23.7 x 15.5 mm ) sized CCD sensor .
Below you can see the D30 and D100 sensor size comparison.
Canon D30 and Nikon D100 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.