Andy,
I've been researching the very same thing over the last couple of days and it seems you'll need the X-pro series as they go down to 15mm on a 5D.
That may be the info provided Bob, but from a real life example, i've had vignetting at 17mm on the 1Ds mk2 with the X-pro ND8 and the 17-40 f/40. :shrug:
So for wide angle landscape work it's not going to be much good then.
Jon,
From what I've read, the 17-40 will vignette on a full frame regardless of whether it has a filter or not.....
There is actually a special holder designed for use with wide angle lenses (only has slot for one filter though) so I wonder if that solves the problem. I might just go ahead and bite the bullet to find out that way. Look out for a set of second hand filters on the forum in the coming months
Which reminds me, you can hack off the additional holder part of the cokin holders.
just noticed! lolHence the title above my avatar when I made the mistake of asking how to do so!!