Both Sony A9 and Sony A7 have Full frame sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the A9 and A7 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A9 and Sony A7 Cameras
Sony A9 and Sony A7 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 Sony A9 and Sony A7 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, A9 has scored 92, 2 points higher than A7.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A9
92
24.9 bits
13.3 Evs
3517 ISO
Sony A7
90
24.8 bits
14.2 Evs
2248 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
Sony A9
or the
Sony A7 ,
including hyperfocal distance.
