Excerpt: This is a great L series lens. The images are very sharp even with wide open aperture. Lack of IS is noticeable when shooting indoor handheld at low light. But I got this lens for my landscape photography and IS is not required as I'm shooting with Tripod. Barrel distortion is quite big at the widest focal length but can be corrected somewhat in Photoshop/Light Room, just need to avoid putting people at the edge while shooting 17mm.
Pros: Durable, Fast / accurate auto-focus, Strong Construction
Excerpt: I am exploring with this lens, so far I love it. Landscapes, group shots, and portrait. It is clear, fast and great all around for the price. I love the versatility of this lens. Happy I bought it.
Pros: Durable, Fast / accurate auto-focus, Rugged, Strong Construction
Excerpt: The 17-40L is often noted for having soft edges/corners at wider apertures, and this is true. However, stop the lens down and performance is stellar.Color and contrast are incredible. I have used the 16-35 II, 14L II and third part options as well... The 17-40L remains my favorite.The 16-35 II offers nothing except for the f/2.8 over the 17-40 at double the cost.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Lightweight, Rugged
Excerpt: I needed a wider lens than my 24-70 for various situations (landscape, architecture etc...) so I purchased this 17-40 f/4. It is a compact, light, half the price of the faster 16-35 and an overall great lens. I was surprised how much I enjoyed using it right from the start. It was essential for capturing the beautiful landscape in Iceland. I do not have any complaints about this lens at the moment.
Pros: Easily Interchangeable, Fast / accurate auto-focus, Lightweight