Canon SX10 IS has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . 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 .
Below you can see the SX10 IS and SX40 HS sensor size comparison.
Canon SX10 IS and Canon SX40 HS have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.