Both Canon 20D and Canon 350D have APS-C sized 8.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Below you can see the 20D and 350D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 20D and Canon 350D Cameras
Canon 20D and Canon 350D 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 Canon 20D and Canon 350D 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, 20D has scored 62, 2 points higher than 350D.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 20D
62
21.9 bits
11.0 Evs
721 ISO
Canon 350D
60
21.8 bits
10.8 Evs
637 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 20D
or the
Canon 350D ,
including hyperfocal distance.
