Sony A7 II has a
24.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor. On the other hand, Sony A9 III has a
24.6MP Full frame (35.6 x 23.8 mm ) sized Global Shutter sensor and features BIONZ XR processor.
One other difference between these two cameras that is worth mentioning is that Sony A9 III'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 A7 II and A9 Mark III sensor size comparison.
Sensor Size and Resolution Comparison image of Sony A7 II and Sony A9 III Cameras
Sony A7 II and Sony A9 III 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 A7 II and Sony A9 III 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, A7 II has scored 90, 3 points higher than A9 Mark III.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Sony A7 II
90
24.9 bits
13.6 Evs
2449 ISO
Sony A9 III
87
24.1 bits
13.0 Evs
3224 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 A7 II
or the
Sony A9 III ,
including hyperfocal distance.
