I bought this lens after contemplating buying the new 16-35 2.8. I had the money to buy the more expensive lens but I didn't and here is why. I was told by an aquaintance who test for Canon that the 17-40 f 4.0 is over all sharper and has less distortion than the new 16-35 f 2.8 (as of Aug 15 2007). I have heard this from other photographers as well. Also although it isn't an f 2.8 as like the 16-35 it does have a bit more range and I have found the focusing is pretty fast regardless. I think it is the best $700 I ever spent on a piece of camera equipment.

The EF 17-40 will not give you f/2.8, and at f/4 it is not the sharpest. Even so, with a tripod at f/5.6 to f/8 and beyond it is a match for the EF 16-35. Therefore, although as a walk-around lens it cannot compare to the more expensive lenses, if you want to do landscapes, it is by far the best buy in the wide angle L series of Canon--and it will not be bested by the EF 16-35 at the apertures where it is most likely to be used for landscape photography. Combined with its light weight, it is ideal for packing into the mountains or other back country.I would like to give it five stars, but its limitations at f/4 would make that less than honest.

The camera is a beauty! Especially paired with the 16-35 f/2.8 version iii (The only lens I have right now). I just switched over from the sony a6300 and the quality/ease-of-use is night and day! If you are recording video in 4k make sure you get a FAST memory card that can handle the high bitrate on this camera. I recommend anything with at least 300 MB/s with v90 (Lexar 2000x or the TOUGH Sony G series cards). I shoot music videos and do youtube sit-downs, being able to shoot 4k with the high bitrates is nice!

Love it! goes very well with my 12-35 f 2.8 lumix glass

I love the image quality I get from this filter, I use it with my canon 16-35

better than the 16-35..........but you 16-35 owners wouldn't understand why

I have the 16-35mm F4, and indeed the extra 2mm help a bit....but as far as IQ I can't say there is much of a difference.If you have already a canon 16-35mm f4, then there is no need to get this one ( I got it because the 16-35 is now under my wife's fingernails)The 15-35 f2.8 it's different story, if indeed you need 2.8, but same applies to the 2.8 EF variant - 1mm difference.In sum, a great lens, way more compact than my 11-24mm, similar performer as the superb EF16-35mm f4, but as a first UWA or replacement from a 17-40 for instanceRecommended

It tried this lens after my 16-35/f2.8 was stolen. It's a great value compared to Canon's other L series lenses. If you don't need the extra speed of the 2.8 lens, I highly recommend it. The only possible con I could come up with is that it is very light compared to the 16-35, which could imply something about its durability, but that's pure conjecture, and I can't subtract a star for that. It could simply be that the 16-35 contains more glass to accomplish the 2.8 aperture.