Both Canon 77D and Sony A77 have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the 77D and A77 sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 77D and Sony A77 Cameras
As seen above, Sony A77 has a 1.1x Larger sensor area than Canon 77D. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.
DxOMark Sensor Scores
At Camera Decision, we also look at Dxo Mark sensors when available as we think it is a good indicator of image quality.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 77D
78
23.6 bits
13.3 Evs
971 ISO
Sony A77
78
24.0 bits
13.2 Evs
801 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
Canon 77D
or the
Sony A77 ,
including hyperfocal distance.
