Canon SD970 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Olympus SH-1 has a
16.0MP 1/2.3' (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features TruePic VII processor.
Below you can see the SD970 IS and SH-1 sensor size comparison.
Canon SD970 IS and Olympus SH-1 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 SD970 IS has 32% larger pixel area compared to Olympus SH-1, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.