Nikon D850 has a
46.0MP Full frame (35.9 x 23.9 mm ) sized BSI-CMOS sensor and features Expeed 5 processor. On the other hand, Sony A7S has a
12.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor.
Nikon D850's sensor provides 34MP 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.
Another difference between these two cameras is that Nikon D850'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 D850 and A7S sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon D850 and Sony A7S Cameras
Nikon D850 and Sony A7S have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
DxOMark Sensor Scores
Both Nikon D850 and Sony A7S 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, D850 has scored 100, 13 points higher than A7S.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon D850
100
26.4 bits
14.8 Evs
2660 ISO
Sony A7S
87
23.9 bits
13.2 Evs
3702 ISO
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Nikon D850
or the
Sony A7S ,
including hyperfocal distance.
