You asked
Best camera for the canon ef 17 40mm f 4l usm?
The 17-40mm f/4L was made for full frame, so I'd pair it with a full-frame body. My top pick is the Canon EOS 5D Mark IV, which lets the lens show its full wide-angle range. If you want something lighter, the Canon EOS 6D Mark II is a sensible partner for the same lens.
On an APS-C body the lens still works, but it frames more like 27-64mm, so you lose most of the wide end. If you're on a budget and happy with that crop, the Canon EOS 80D is the one I'd choose. Not sure which sensor size suits you? Have a look at sensor sizes.
Written by Claude from this site's pages.