Excerpt: This is what I use for interiors and landscape. Best if focused manually. I have a 5DIII and use magic lantern which gives you focus peaking (plus a lot more) on the 5DIII and that makes critical focus easy to achieve. The lens produces very good colors and detail if used at f/ or f/11 especially. Worth every cent.
Excerpt: I use this lens as an all-purpose lens, since I have an APS-C body (equivalent FoV of 25.2-64mm). It is very light, so makes a perfect walk-around lens. This is my first L-series lens and it feels great! It feels solid, the zoom and focus rings move very smoothly. The autofocus is fast and accurate and the image quality is great. Images are sharp and, at least on a cropped APS-C sensor, show little vignetting.
Pros: Consistent Output, Fast / accurate auto-focus, Lightweight, Strong Construction
Excerpt: I've owned both the 16-35/2.8 and this lens. If you don't need the extra aperture of the 16-35, the 17-40 is a much better value. I use it on a full-frame camera (1D-X) and couldn't be more pleased with it. I use it primarily for sports (Basketball) and landscapes.
Excerpt: We use this beautiful lens for documentary filmmaking - on the Blackmagic Design Production Camera 4k. No wonder this lens is much loved. It's a piece of glass that handles light, and color along the full range without much if any flare, or chromatic aberration.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Strong Construction
Excerpt: I purchased the 17-40mm f/4L lens for real estate photography. So far it has exceeded all of my expectations. It's perfect for anything you plan to shoot wide, may that be real estate or landscapes. I have nothing bad to say about this lens, it performs very well for the price!