Olympus VG-160 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Panasonic ZS40 has a
18.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Venus Engine processor.
Below you can see the VG-160 and ZS40 sensor size comparison.
Olympus VG-160 and Panasonic ZS40 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 Olympus VG-160 has 30% larger pixel area compared to Panasonic ZS40, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.