Panasonic FX48 has a 12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Panasonic FH5 has a 16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine IV processor.
Below you can see the FX48 and FH5 sensor size comparison.
Panasonic FX48 and Panasonic FH5 have 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 FX48 has 32% larger pixel area compared to Panasonic FH5, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.