Both Panasonic GH1 and Nikon D5000 have 12.0 MP resolution sensors but Panasonic GH1's sensor is Four Thirds (18.89 x 14.48 mm ) and Nikon D5000's sensor is APS-C (23.6 x 15.8 mm ).
Since Nikon D5000'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 Panasonic GH1.
Below you can see the GH1 and D5000 sensor size comparison.
Sensor Size and Resolution Comparison image of Panasonic GH1 and Nikon D5000 Cameras
As seen above, Nikon D5000 has a 1.4x Larger sensor area than Panasonic GH1. 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.
DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. It scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Panasonic GH1 and Nikon D5000 sensors have been tested by DxO and the results show that D5000 has a better overall score of 72, 8 points higher compared to GH1's score of 64.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Panasonic GH1
64
21.6 bits
11.6 Evs
772 ISO
Nikon D5000
72
22.7 bits
12.5 Evs
868 ISO
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
Panasonic GH1
or the
Nikon D5000 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds versus APS-C),
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.
