Canon 24-70mm EF f/2.8L USM Lens
Replacing the venerable EF 24-70mm f/2.8L lens a few years ago, the new EF 24-70mm f2.8L II lens bests the original in every respect that matters for image quality. The price is significant, but this pick is also going to be the lens you probably keep mounted on your camera the most. It covers an essential range for a walk-around lens, and should meet most needs for convenience and performance from wide to telephoto.
Walk-around lenses are generally defined as a do-it-all lens that lets you capture wide shots as well as short telephoto. The Canon EF 24-70mm f/2.8L II will not only do that, but accomplish this better than any other similarly spec'd lens, sometimes by a large margin.
For the longest time, the sharpest lens for Canon cameras was the TS-E 24mm f/3.5L II tilt-shift lens by Canon with edge-to-edge sharpness that was legendary. However, it's not "fast," which is to say its aperture does not let in enough light to categorize it as fast since fast lenses are considered to be f/2.8 or larger. And the TS-E 24mm is doesn’t auto-focus nor does it zoom, instead being a purpose built prime lens designed for a limited use, namely perspective correction. The Canon EF 24-70mm f/2.8L II, on the other hand, is even sharper at 24mm. It is the new Canon sharpness king because not only is it sharper at 24mm, but it zooms out to 70mm, auto-focuses, and performs at a fast f/2.8!
Utilizing Super UD and aspherical elements in the new optical formula, the 24-70mm f/2.8L II is razor sharp across its entire range. There is currently no zoom lens sharper across its range. As a walk-around lens, this lens is the champion. As a supremely performing professional lens for more specific needs (like fashion photography for instance) this lens is without equal for those seeking a one two punch of convenience and performance.
As with most professional level lenses, the 24-70mm f/2.8L II uses 9 round aperture blades to achieve that gorgeous bokeh effect, where out of focus objects melt away into a smooth, pleasing blur, so prized by professionals and amateurs alike. Granted, it's a touch on the heavy side since fast zoom lenses require large optical elements which weigh a considerable amount, but that's really the only knock against this lens. In fact, the front element, and many of the internal elements are so weighty, Canon included a zoom lock switch to prevent the lens from physically extending as it rests facing down by your side when not in use or when being transported.
Okay, there might be one more shortcoming and it's the price. No fast, professional zoom is cheap but even by those standards, the 24-70mm f/2.8L II commands a premium cost. It doesn't have image stabilization which would help explain its price tag, but would also increase the lens' weight and bulk were it included. All said it's also worth every penny. Few lenses master as many important criteria for a lens as well as the EF 24-70mm f/2.8L II USM lens does. If you consider that this lens will likely outlast your next 3 or 4 cameras, it's an investment that will eventually pay for itself.