Both Kodak Z915 and Canon 400D have 10.0 MP resolution sensors but Kodak Z915's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Canon 400D's sensor is APS-C (22.2 x 14.8 mm ).
Since Canon 400D'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 Kodak Z915.
Below you can see the Z915 and 400D sensor size comparison.
As seen above, Canon 400D has a 11.7x Larger sensor area than Kodak Z915. 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.