Sigma DP2 Quattro has a 20.0MP APS-C (23.5 x 15.7 mm ) sized CMOS (Foveon X3) sensor and features TRUE III engine processor. On the other hand, Canon SX40 HS has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Sigma DP2 Quattro's sensor provides 8MP more than Canon SX40 HS'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 DP2 Quattro and SX40 HS sensor size comparison.
![Sigma DP2 Quattro vs Canon SX40 HS Sensor Size Comparison]()
Sensor Size and Resolution Comparison image of Sigma DP2 Quattro and Canon SX40 HS Cameras
As seen above, Sigma DP2 Quattro has a 13.1x Larger sensor area than Canon SX40 HS. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.