Both Pentax K-3 II and Sony A7 II have 24.0 MP resolution sensors but Pentax K-3 II's sensor is APS-C (23.5 x 15.6 mm ) and Sony A7 II's sensor is Full frame (35.8 x 23.9 mm ).
Since Sony A7 II'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 Pentax K-3 II.
Another difference between these two cameras is that Pentax K-3 II'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 K-3 II and A7 II sensor size comparison.
As seen above, Sony A7 II has a 2.3x Larger sensor area than Pentax K-3 II. 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. Pentax K-3 II and Sony A7 II sensors have been tested by DxO and the results show that A7 II has a better overall score of 90, 10 points higher compared to K-3 II's score of 80.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Pentax K-3 II |
80 |
23.6 bits |
13.6 Evs |
1106 ISO |
Sony A7 II |
90 |
24.9 bits |
13.6 Evs |
2449 ISO |