 The IS system of the 17–55 gives that lens an advantage over the 24–70 2.8 in lower light by reducing the amount of camera shake.The 17–55 and the 24–70 4 are both stabilized, but the 17–55 has a one-stop advantage over that version of the 24–70.The EF 28–90mm, though having corresponding full-frame equivalent focal length, is an inexpensive kit lens and is not comparable to the 17–55mm, having slower aperture, a variable maximum aperture, lower image quality, and no image stabilization.