Both Canon SX740 HS and Kodak Astro AZ651 have 21.0 MP resolution sensors but Canon SX740 HS's sensor is 1/2.3 (6.17 x 4.55 mm ) and Kodak Astro AZ651's sensor is (1/2. ).
Since Canon SX740 HS'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 Astro AZ651.
Below you can see the SX740 HS and Astro AZ651 sensor size comparison.
As seen above, Canon SX740 HS has a infx Larger sensor area than Kodak Astro AZ651. 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.