The phot r et 65b compatible canon lens hood helps to prevent unwanted stray light from entering the lens by shading the front of the lens dedicated lens hoods are designed to match the specific focal length of the lens it was designed for since the end of the lens is extended you also get the added benefit of some extra protection from accidental impact dedicated lens hoods are designed to match the specific focal length of the lens it was designed for this lens hood is compatible with can