Canon 40D has a
10.0MP APS-C (22.2 x 14.8 mm ) sized CMOS sensor . On the other hand, Canon 70D has a
20.0MP APS-C (22.5 x 15 mm ) sized CMOS sensor and features Digic 5+ processor.
Canon 70D's sensor provides 10MP more than Canon 40D'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 40D and 70D sensor size comparison.
Canon 40D and Canon 70D 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
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 40D and Canon 70D sensors have been tested by DxO and the results show that 70D has a better overall score of 68, 4 points higher compared to 40D's score of 64.
Model |
Overall |
Color Depth |
Dynamic Range |
Low-light ISO |
Canon 40D |
64 |
22.1 bits |
11.3 Evs |
703 ISO |
Canon 70D |
68 |
22.5 bits |
11.6 Evs |
926 ISO |