Both Nikon D4 and Olympus SP-620 UZ have 16.0 MP resolution sensors but Nikon D4's sensor is Full frame (36 x 23.9 mm ) and Olympus SP-620 UZ's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Nikon D4'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 Olympus SP-620 UZ.
Below you can see the D4 and SP-620 UZ sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D4 and Olympus SP-620 UZ Cameras
As seen above, Nikon D4 has a 30.7x Larger sensor area than Olympus SP-620 UZ. 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
Nikon D4
or the
Olympus SP-620 UZ ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Full frame versus 1/2.3-inch),
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.
