Both Samsung EX2F and Canon SX40 HS have 12.0 MP resolution sensors but Samsung EX2F's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Canon SX40 HS's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Samsung EX2F's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Canon SX40 HS.
Below you can see the EX2F and SX40 HS sensor size comparison.
As seen above, Samsung EX2F has a 1.5x 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.