Both Sony A57 and Panasonic G5 have 16.0 MP resolution sensors but Sony A57's sensor is APS-C (23.5 x 15.6 mm ) and Panasonic G5's sensor is Four Thirds (17.3 x 13 mm ).
Since Sony A57'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 G5.
Below you can see the A57 and G5 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A57 and Panasonic G5 Cameras
As seen above, Sony A57 has a 1.6x Larger sensor area than Panasonic G5. 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
Both Sony A57 and Panasonic G5 sensors have been tested by DxoMark. DxoMark 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. Of the two cameras that we are comparing, A57 has scored 75, 14 points higher than G5.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A57
75
23.4 bits
13.0 Evs
785 ISO
Panasonic G5
61
21.4 bits
11.6 Evs
618 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
Sony A57
or the
Panasonic G5 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(APS-C versus Four Thirds),
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.
