Both Sony A77 II and Pentax K-3 have 24.0 MP resolution sensors but Sony A77 II's sensor is APS-C (23.5 x 15.6 mm ) and Pentax K-3's sensor is APS-C (23.5 x 15.6 mm ).
Since Pentax K-3'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 Sony A77 II.
One other difference between these two cameras that is worth mentioning is that Pentax K-3'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 A77 II and K-3 sensor size comparison.
Sony A77 II and Pentax K-3 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
DxOMark Sensor Scores
Both Sony A77 II and Pentax K-3 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, A77 II has scored 82, 2 points higher than K-3.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Sony A77 II |
82 |
24.4 bits |
13.4 Evs |
1013 ISO |
Pentax K-3 |
80 |
23.7 bits |
13.4 Evs |
1216 ISO |