Review by Klaus Schroiff, published March 2013

Special thanks to Keith Bannett for providing this lens for testing purposes!

Introduction

The build quality of this lens is exceptional thanks to a tightly assembled combination of metal and high quality plastic parts. Both zoom and focus ring operate smoothly. The lens is designed to survive in harsh conditions due to sealings against dust and moisture. Typical for most standard zoom lenses, it extends when zooming towards the long end of the range. The front element doesn't rotate, of course. The slower max. aperture allows a more compact design - the EF 24-70mm f/4 USM L IS is about 25% smaller and more light-weight than its f/2.8 cousin. However, it's still a fairly big lens when thinking of the old (discontinued), consumer grade Canon EF 24-85mm f/3.5-4.5 USM for instance.

Typical for a professional grade Canon lens, the AF is based on a ring-type USM (ultrasonic) with FTM (full-time manual focusing). The AF is both speedy as well as virtually silent. The Live View AF performance is about average (thus slowish). The AF accuracy of the tested sample was fine at fully open aperture but not that hot beyond - more on this later.

Canon image stabilizers are very mature by now so it's no surprise that it achieves at least 3 f-stops in standard situations whereas the efficiency deteriorates towards very close focus distance (which is normal). "Very close" is also a serious statement here because the lens has a max. magnification ratio of 1:1.4 which rivals macro lenses - on paper at least.

Here’s how the specs compare against its two in-house mates: