Both Sigma SD9 and Nikon D1H have APS-C sized 3.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another difference between these two cameras is that Sigma SD9's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the SD9 and D1H sensor size comparison.
Sensor Size and Resolution Comparison image of Sigma SD9 and Nikon D1H Cameras
As seen above, Nikon D1H has a 1.3x Larger sensor area than Sigma SD9. 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
Sigma SD9
or the
Nikon D1H ,
including hyperfocal distance.
