"It comes with a lens that goes to 560mm equivalent optical zoom."
OK, now we need to explain some technical stuff.
The Canon SX20IS comes with a 5 to 100mm zoom lens, it uses a 1/2.3 size sensor which means it has a "crop factor" of 5.6.
The crop factor refers to the sensor size as compared to a 35mm frame size. In this case the sensor is (much) smaller than a 35mm frame which means the image will be cropped by the smaller size of the sensor.
They call it a 28 to 560mm "equivalent" because 5mm x 5.6(the crop factor) = 28 and 100mm x 5.6 = 560, so it is not really a 28 to 560mm zoom it is a 5 to 100mm zoom "cropped" to the "equivalent" of a 28 to 560mm zoom (which is intentionally misleading).
Buyer beware!
