The Canon EF 17-40mm f/4L USM Lens is an affordable L series wide angle lens, not quiet the sweet spot of the Canon 16-35mm lens but a great priced option. It offers the choice of a using a normal screw-in 77mm filter or a holder in the rear of the lens for up to three gel filters. On your cropped sensor camera its going to give you an equivalent focal length of 27mm to 64mm.
