Canon A2200 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features DIGIC 4 with iSAPS technology processor. On the other hand, Canon A3100 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the A2200 and A3100 IS sensor size comparison.
Canon A2200 and Canon A3100 IS 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.