The EW-83L Lens Hood from Canon is a petal-style lens hood designed specifically for the EF 24-70mm f/4L IS USM lens. A lens hood's primary purpose is to block stray light from entering the lens and causing unwanted flare. A dedicated lens hood is shaped specifically to fit the focal length of the lens for which it is designed. The petal shape of this lens hood maximizes the amount of hood coverage without intruding into the frame. In addition to deflecting unwanted light a lens hood will offer the lens a degree of protection from accidental impact and the elements.