Off on holidays to France and want opinions on the best wide angle for my 5D. Bit confused about angle I get off FF on EF-S lens. Is it at 10mm I dont get 10mm because lens adjusts itself for non FF cameras? Appreciate advice on both canon and non canon that gives me the best IQ. Thanks.

What is your budget? Do you prefer Canon to other brands?I use Canon 16-35 with 5D and I'm pretty happy with the combination. 16-35 seems to a standard in wide zooms, while 17-40 gives perhaps similar pictures for much less. If the budget is not concern, go for 16-35.

The 5D won't accept an EF-S lens. The previous post had some good suggestions. I'm very happy with my Sigma 12-24. Right now it's the widest of the wide and designed for FF. Shots, like inside St. Peters/Vatican, it's truly amazing. -- 'We shall not cease from exploration And yet the end of all our exploring Will be to arrive where we started And know the place for the first time.' T.S. Eliot

I like the Canon 35lL f1.4. It is very pricey, but not that much more than a 16-35 2.8 zoom and it is far superior. The 1.4 is very useful in generating background blur, which is a very nice, pleasing effect with wide angle shots. This is because the wide lenses generally pickup very cluttered and busy backgrounds due to the wide view and you often have little control over the background of an image the way you do with telephoto (which is generally easier to blur or change with your shooting position).the 35mm helps me eliminate much of this annoying detail and focus image on the subject at hand.I is also nice in low light (although even in bright light, I almost always shoot it wide open for the effect I just mentioned.)I find I rarely need zoom with wide lenses since I can easily step back and forth a foot or two and get the same framing as the zoom would have given me since my subjects are generally rather close in.