The original hood that comes with EF lenses are ideal on Full Frame
DSLR. However when these lenses are mounted onto a non full frame DSLR,
the original hood does not provide sufficient shield due to the camera
crop factor. i.e. 17-40mm lens becomes 27-64mm, but still on a 17-40mm
EW-83J was originally made for EFS 17-55 f2.8, the equivalent of full
frame is 27-88mm.
When EW-83J is mounted on EF lens, the protection is very much better
due to the larger hood petal.
It is tested successfully without vignetting using EOS300D on EF17-40L
* EFS 17-55 f2.8
* EF 20-35mm f/3.5-4.5L
* EF 17-35mm f/2.8L
* EF 17-40mm f/4L USM
* EF 24-105mm f/4L IS USM