Panasonic ZS8 has a
14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine FHD processor. On the other hand, Panasonic ZS3 has a
10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the ZS8 and ZS3 sensor size comparison.
Panasonic ZS8 and Panasonic ZS3 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 ZS3 has 40% larger pixel area (2.78µm2 vs 1.98µm2) compared to Panasonic ZS8, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.