Canon SD940 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor. On the other hand, Canon SD1400 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the SD940 IS and SD1400 IS sensor size comparison.
Canon SD940 IS and Canon SD1400 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.