Panasonic ZS3 has a
10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Panasonic FX75 has a
14.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine HD II processor.
Below you can see the ZS3 and FX75 sensor size comparison.
Panasonic ZS3 and Panasonic FX75 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 compared to Panasonic FX75, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.