Canon SD3500 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor. On the other hand, Canon N Facebook ready has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features Digic 5 processor.
Below you can see the SD3500 IS and N Facebook ready sensor size comparison.
Canon SD3500 IS and Canon N Facebook ready 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. On the other hand, since Canon N Facebook ready has 55% larger pixel area (3.12µm2 vs 2.01µm2) compared to Canon SD3500 IS, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.