Both Sony A9 and Nikon D750 have 24.0 MP resolution sensors but Sony A9's sensor is Full frame (35.6 x 23.8 mm ) and Nikon D750's sensor is Full frame (35.9 x 24 mm ).
Since Nikon D750'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 Sony A9.
Below you can see the A9 and D750 sensor size comparison.
Sony A9 and Nikon D750 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
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 A9 and Nikon D750 sensors have been tested by DxO and the results show that D750 has a better overall score of 93, 1 points higher compared to A9's score of 92.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Sony A9 |
92 |
24.9 bits |
13.3 Evs |
3517 ISO |
Nikon D750 |
93 |
24.8 bits |
14.5 Evs |
2956 ISO |