Canon A490 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Canon SX170 IS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Canon SX170 IS's sensor provides 6MP more than Canon A490's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the A490 and SX170 IS sensor size comparison.
Sensor Size and Resolution Comparison image of Canon A490 and Canon SX170 IS Cameras
Canon A490 and Canon SX170 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. On the other hand, since Canon A490 has 59% larger pixel area compared to Canon SX170 IS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Canon A490
or the
Canon SX170 IS ,
including hyperfocal distance.
