With the 11-24mm F/4L USM Canon’s engineers have constructed one of the best wideangle zooms ever made. The world’s widest rectilinear zoom provides class-leading image quality, with exceptional sharpness at all settings even on high resolution sensors. Distortion, chromatic aberration and vignetting are all kept reasonably low. Construction is superb, with weather sealing for outdoor use, and the autofocus is fast and silent. Full-frame users specialising in landscape, architectural or interior photography who demand exceptional optical performance need look no further. It’s bulky and expensive, but for those who can afford it, it’s an absolutely outstanding piece of glass.