Olympus SZ-31MR iHS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Dual TruePic V processor. On the other hand, Panasonic ZS70 has a
20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine processor.
Below you can see the SZ-31MR iHS and ZS70 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus SZ-31MR iHS and Panasonic ZS70 Cameras
Olympus SZ-31MR iHS and Panasonic ZS70 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.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Olympus SZ-31MR iHS
or the
Panasonic ZS70 ,
including hyperfocal distance.