The
Canon EW-83J Lens Hood,
like all other Lens hoods, is
primarily designed to prevent
unwanted stray light from
entering the lens by extending
and shading the end of the lens.
In addition, since the end of
the lens is extended, you also
get the added benefit of some
extra protection from accidental
impact.
The "petal" shape of The EW-83J Lens Hood maximizes the amount of hood coverage for the minimum amount of weight and hood area. This dedicated lens hood is designed to match the specific focal length of the lens it was designed for.