Panasonic GF3 has a
12.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine FHD processor. On the other hand, Panasonic GF7 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine processor.
Below you can see the GF3 and GF7 sensor size comparison.
Panasonic GF3 and Panasonic GF7 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 GF3 has 31% larger pixel area compared to Panasonic GF7, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.