Both Canon 100D and Canon 1200D have APS-C sized 18.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the 100D and 1200D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 100D and Canon 1200D Cameras
Canon 100D and Canon 1200D 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
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 100D
63
21.8 bits
11.3 Evs
843 ISO
Canon 1200D
63
21.9 bits
11.3 Evs
724 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 100D
or the
Canon 1200D ,
including hyperfocal distance.
