The Canon EW-83D lenshood (designed for the 24mm f/1.4L) is an often-suggested, more effective substitute on crop camera bodies for the rather huge and impractical EW-83E hood that is supplied with the 17-40mm f/4L lens. Conventional wisdom is that on full-frame you will indeed have to use the EW-83E to avoid vignetting.

When actually trying the EW-83D on my 5D I saw that it _almost_ worked, it displayed only a very small amount of vignetting at the 17mm end. So - I took out the old Dremel and removed a small bit of material (a couple of millimeters) from the offending petals to get rid of the vignetting. A quick check to verify that the vignetting was, indeed, gone, a rapid going-over with a hand file to prettify things, and now I can use the 17-40 with the EW-83D hood on my 5D sans vignetting!

The whole point of the exercise is that the EW-83E is simply too large in diameter to fit the carrying holsters that I use when I walk around with one lens on and one off camera, it is also rather ineffective as front element protection because of its very wide diameter. With the "D" hood I can now stuff the 17-40 complete with hood into the holster I use for carrying the 24-70L in. This is not possible with the "E".

*** UPDATE *** I recently got myself a 1Ds Mark II to replace the 5D. The sensor on this camera is apparently a bit bigger than the 5D sensor, so I must trim a little bit more off the hood at top and bottom.