Christopher: This lens from what I have seen gets a lot of hype from both photographers and vidoegraphers so I had to give it a try and see what I was missing. I had some pros and cons with this lens. My pro, great for filming in good light. The colors that came out of it between f/5.6 and f/8 were spot-on and it provided a solid picture with a lot of clarity. My major con was pretty simple, this is an L lens and with that should provide L lens quality. With its photo taking ability, wasn't to impressed. The AF was not very quick in a lot of situations and in low light I thought it really struggled getting the clarity and sharpness that I was looking for. In my opinion if you are looking for a wide angle zoom and you have a cropped sensor like myself, try out the 17-55 f/2.8. I thought it crushed the 17-40 f/4L in every aspect.

Nissa: I rented the Canon 17-40mm f4L last year to find out if it would be a good purchase for my wedding photography bag. I shoot full-frame 5Ds, and was looking for something that would cater to the ultra wide shots I needed while still staying under the $1k price range. I don't purchase third party lenses - only Canon - so this seemed to be the perfect solution. I can tell you that I now own the lens - so my review is overall quite favorable - but it doesn't come without a few caveats. I find the 17-40 to be a real pleasure to use. It is light; but feels sturdy in construction. I didn't have any problems with a slow focus, but I have to say that the restriction of this being only an f4 lens definitely keep you shooting in gratuitous light. I found myself using the lens for wide ceremony shots and for wide shots of the dance floor - the former being sunlight and the latter lit with flash. At f4, I am definitely stretching it on a dark dance floor with bounce flash. Color wise, it's definitely an L lens. I found the sharpness to be acceptable/good. One major issue you'll want to take in to consideration, if you are shooting full-frame, is vignetting, which is quite apparent at 17mm. I was able to correct any drop-off using Photoshop. I found myself really enjoying this lens at f8-f11. I do not have experience with wide angle lenses touting the larger f2.8 apertures, but I believe that the 17-40mm f4L is a great lens, if you can shoot at f4 or above. If you're going to have some light, this is the lens for you.

Julian: I am pretty sure the L in Canon L lenses must stand for lovely, because when you get your gear home and download all the photos from your cards, the results with this lens are exactly that! It does not disappoint, it's a gem! Not nearly as hefty as I was expecting, but it's definitely not a small, light lens. You could easily make this lens your 'default' lens and shoot many great photos. If I were to point out one negative (and I am really fishing here) it would have to be that this lens is not great for indoors shots unless the lighting is great, or you're using a flash, but if you go into this knowing that it's an f/4 lens, you'd already assume that you're going to need good lighting. The bokeh is creamy like a french brie, and I would happily rent it again for landscapes, group photos, and general use.