Both Sony A57 and Panasonic GX850 have 16.0 MP resolution sensors but Sony A57's sensor is APS-C (23.5 x 15.6 mm ) and Panasonic GX850'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 GX850.
One other difference between these two cameras that is worth mentioning is that Panasonic GX850's sensor doesn't have an 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 A57 and GX850 sensor size comparison.
As seen above, Sony A57 has a 1.6x Larger sensor area than Panasonic GX850. 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 GX850 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, 2 points higher than GX850.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Sony A57 |
75 |
23.4 bits |
13.0 Evs |
785 ISO |
Panasonic GX850 |
73 |
23.2 bits |
13.3 Evs |
586 ISO |