Both Nikon Z9 and Nikon Z7 have Full frame sized 46.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Nikon Z7'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 Z9 and Z7 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon Z9 and Nikon Z7 Cameras
Nikon Z9 and Nikon Z7 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.
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. Nikon Z9 and Nikon Z7 sensors have been tested by DxO and the results show that Z7 has a better overall score of 99, 1 points higher compared to Z9's score of 98.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Nikon Z9
98
26.3 bits
14.4 Evs
2451 ISO
Nikon Z7
99
26.3 bits
14.6 Evs
2668 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 Z9
or the
Nikon Z7 ,
including hyperfocal distance.
