Sony A850 has a
25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Bionz processor. On the other hand, Sony A99 II has a
42.0MP Full frame (35.9 x 24 mm ) sized BSI-CMOS sensor and features Bionz X processor.
Sony A99 II's sensor provides 17MP more than Sony A850'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 Sony A99 II'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 A850 and A99 II sensor size comparison.
Sony A850 and Sony A99 II 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. On the other hand, since Sony A850 has 72% larger pixel area compared to Sony A99 II, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
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. Sony A850 and Sony A99 II sensors have been tested by DxO and the results show that A99 II has a better overall score of 92, 13 points higher compared to A850's score of 79.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Sony A850 |
79 |
23.8 bits |
12.2 Evs |
1415 ISO |
Sony A99 II |
92 |
25.4 bits |
13.4 Evs |
2317 ISO |