Sony A7R III has a 42.0MP Full frame (35.9 x 24 mm ) sized BSI-CMOS sensor and features Bionz X processor. On the other hand, Sony A850 has a 25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Bionz processor.
Sony A7R III'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.
Another difference between these two cameras is that Sony A7R III'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 A7R III and A850 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A7R III and Sony A850 Cameras
Sony A7R III and Sony A850 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 (35.33µm2 vs 20.43µm2) compared to Sony A7R III, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.
DxOMark Sensor Scores
Both Sony A7R III and Sony A850 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, A7R III has scored 100, 21 points higher than A850.
| Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
|
Sony A7R III |
100 |
26.0 bits |
14.7 Evs |
3523 ISO |
|
Sony A850 |
79 |
23.8 bits |
12.2 Evs |
1415 ISO |