Full Test: Canon EF 16-35mm f/2.8l III
Canon’s top-flight ultra-wide zoom gets a major revamp, following in the footsteps of the 5D Mk IV
A major revamp in every area. Canon’s latest full-frame ultra-wide zoom put through its paces in our lab
now in its third incarnation, Canon’s fast, ultra-wide 16-35mm f/2.8l III USM is one of two upgraded lenses to be launched alongside the much vaunted 5D Mk IV. The other is the more general purpose EF 24-105mm f/4l IS II USM. The new ultra-wide lens is a proper whopper, gaining considerable size and weight compared with its predecessor. Canon has set out to create something rather special in this new lens. It’s a major revamp over the Mk II edition, in pretty much every area. A starring role is played by a new and highly complex large-diameter, double-surface GMO (Glass Moulded) aspherical element. This sits right at the front of the lens, and there’s also a ground aspherical element at the rear. Two UD (Ultra-low Dispersion) elements, inherited from the Mk II, aim to dramatically reduce distortion and colour fringing.
Further improvements include an updated diaphragm with nine (rather than seven) blades, producing a better rounded aperture for enhanced bokeh. The grouping of the lens elements has also been redesigned to give greater resistance to shock and vibration.
Advanced coatings include SWC (Subwavelength Coating) and ASC (Air Sphere Coating) for greater resistance to ghosting and flare, both of which are lacking in the Mk II lens. It’s a worthy improvement, given the suitability of ultra-wide lenses for landscape photography with big skies. A fluorine coating added to the front and rear elements repels moisture and muck.
Build quality is simply excellent, with a robust and comprehensively weather-sealed construction. Focusing is fully internal, so the
Canon has set out to create something rather special. It’s a major revamp in every area
front element neither extends nor rotates. The overall physical length remains fixed while zooming, but the front element comes closer to the front of the outer barrel at both ends of the zoom range.
Performance
One of our criticisms of the Mk II lens is that sharpness is lacklustre towards the edges and corners of the frame. The Mk III does hugely better, delivering excellent sharpness across the whole frame, along with superb contrast, even when shooting wide-open at f/2.8. However, sharpness and contrast aren’t significantly improved over the EF 16-35mm f/4l IS USM, which we rate as one of Canon’s sharpest ever lenses, and that lens also features image stabilization.
At the short end of the zoom range, there’s a dramatic reduction in the amount of distortion and colour fringing, compared with the Mk II lens. Here again, though, there are no real improvements over the f/4 lens. Ghosting and flare are well controlled by the new coatings, while action shots benefit from fast autofocus speeds, enabled by a new high-performance processor.
As you’d expect from a fast, wide-angle zoom lens, vignetting (darkened image corners) is very noticeable when shooting wideopen, but mostly dies away when stopping down to f/5.6. This is the case throughout the zoom range.