Panasonic G7 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Panasonic G1 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor .
Below you can see the G7 and G1 sensor size comparison.
Panasonic G7 and Panasonic G1 have the same 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 Panasonic G1 has 31% larger pixel area (18.74µm2 vs 14.21µm2) compared to Panasonic G7, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.