Both Nikon D300S and Nikon S3000 have 12.0 MP resolution sensors but Nikon D300S's sensor is APS-C (23.6 x 15.8 mm ) and Nikon S3000's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Nikon D300S'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 Nikon S3000.
Below you can see the D300S and S3000 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D300S and Nikon S3000 Cameras
As seen above, Nikon D300S has a 13.3x Larger sensor area than Nikon S3000. 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 D300S
or the
Nikon S3000 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(APS-C 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.