Both Canon 450D and Canon 1100D have APS-C sized 12.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the 450D and 1100D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 450D and Canon 1100D Cameras
Canon 450D and Canon 1100D 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. Canon 450D and Canon 1100D sensors have been tested by DxO and the results show that 1100D has a better overall score of 62, 1 points higher compared to 450D's score of 61.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 450D
61
21.9 bits
10.8 Evs
692 ISO
Canon 1100D
62
21.9 bits
11.0 Evs
755 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 450D
or the
Canon 1100D ,
including hyperfocal distance.
