Both Pentax P80 and Nikon D3S have 12.0 MP resolution sensors but Pentax P80's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Nikon D3S's sensor is Full frame (36 x 23.9 mm ).
Since Nikon D3S'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 P80.
Below you can see the P80 and D3S sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax P80 and Nikon D3S Cameras
As seen above, Nikon D3S has a 30.7x Larger sensor area than Pentax P80. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in 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 P80
or the
Nikon D3S ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(1/2.3-inch versus Full frame),
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.
