Both Pentax RZ18 and Nikon P1100 have 16.0 MP resolution sensors but Pentax RZ18's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Nikon P1100's sensor is (6.17 x 4.55 mm ).
Since Nikon P1100'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 Pentax RZ18.
Below you can see the RZ18 and P1100 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax RZ18 and Nikon P1100 Cameras
Pentax RZ18 and Nikon P1100 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
Pentax RZ18
or the
Nikon P1100 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/2.3-inch versus ),
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.