Did an event recently with 24-105 f4 and had lens hood on, but came home and noticed a lot of the photos had black vignetting @ 24mm and I could only crop out so much of it, so is there a lens hood that doesn't show vignetting?
I forgot to mention I have a plain UV filter just to protect the glass, so that could be it too. I'll look at shifting the hood around as well, thanks.
Not sure which version you have, but I previously tested the MkI version of the 24-105/4L and found you can stack two standard UV filters without a significant increase in vignetting, so I doubt it's your filter.
The dedicated hood for the 24-105 Mk1 is the EW-83H, but there are many EW-83 hoods (they're up to M at least) that will physically mount on the lens.
There is no chance of vignetting with the appropriate dedicated hood properly mounted.
I find that the 24-105mm f/4L IS still has quite a lot of vignetting at 24mm, even after profile corrections in Lightroom/ACR: are you sure that it isn't just this that you're seeing?