Both Panasonic LZ20 and Nikon L840 have 16.0 MP resolution sensors but Panasonic LZ20's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Nikon L840's sensor is 1/2.3' (6.17 x 4.55 mm ).
Since Nikon L840's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Panasonic LZ20.
Below you can see the LZ20 and L840 sensor size comparison.
Sensor Size and Resolution Comparison image of Panasonic LZ20 and Nikon L840 Cameras
Panasonic LZ20 and Nikon L840 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the 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
Panasonic LZ20
or the
Nikon L840 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/2.3-inch versus 1/2.3' ),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.