Sony A7S has a 12.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor. On the other hand, Pentax K-3 has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features Prime III processor.
Pentax K-3's sensor provides 12MP more than Sony A7S's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
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 moire occurring in certain scenes.
Below you can see the A7S and K-3 sensor size comparison.
![Sony A7S vs Pentax K-3 Sensor Size Comparison]()
Sensor Size and Resolution Comparison image of Sony A7S and Pentax K-3 Cameras
As seen above, Sony A7S has a 2.3x Larger sensor area than Pentax K-3. 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 A7S 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, A7S has scored 87, 7 points higher than K-3.
| Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
|
Sony A7S |
87 |
23.9 bits |
13.2 Evs |
3702 ISO |
|
Pentax K-3 |
80 |
23.7 bits |
13.4 Evs |
1216 ISO |