Canon 40D has a
10.0MP APS-C (22.2 x 14.8 mm ) sized CMOS sensor . On the other hand, Canon 20D has a
8.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor .
Below you can see the 40D and 20D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 40D and Canon 20D Cameras
Canon 40D and Canon 20D 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 40D and Canon 20D 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, 40D has scored 64, 2 points higher than 20D.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 40D
64
22.1 bits
11.3 Evs
703 ISO
Canon 20D
62
21.9 bits
11.0 Evs
721 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 40D
or the
Canon 20D ,
including hyperfocal distance.
