Canon 70D has a
20.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor and features Digic 5+ processor. On the other hand, Canon 20D has a
8.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor .
Canon 70D's sensor provides 12MP more than Canon 20D's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the 70D and 20D sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 70D and Canon 20D Cameras
Canon 70D and Canon 20D 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. On the other hand, since Canon 20D has 143% larger pixel area (41.21µm 2 vs 16.91µm 2 ) compared to Canon 70D, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.
DxOMark Sensor Scores
Both Canon 70D 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, 70D has scored 68, 6 points higher than 20D.
Model
Overall
Color Depth
Dynamic Range
Low-light ISO
Canon 70D
68
22.5 bits
11.6 Evs
926 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 70D
or the
Canon 20D ,
including hyperfocal distance.
