The Canon ET-138WII Lens hood is primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the 600mm f4L IS II lens.
In addition, since the end of the lens is extended, you also get the added benefit of some extra protection from accidental impact. Lens hoods are more prominent in telephoto lenses because the field of view has a smaller viewing angle than of wide-angle lenses. For wide angle lenses, the length of the hood (away from the end of the lens) cannot be as long as those for telephoto lenses because of the viewing angle.
Compatible with the following Canon lens
|Comapatibility||Canon EF 600mm F4 IS II USM|
Canon ET-138WII Lens hood for EF 600mm f4L IS II