Sigma 24-70mm f/2.8 DG OS HSM Art
Does this standard zoom succeed at offering top-level performance for today’s era of highresolution cameras? Michael Topham finds out
Michael Topham tests this stunning standard zoom
Full-frame DSLR and mirrorless camera users have a tough decision to make when choosing a standard zoom. Opt for one that covers a focal length of around 24-105mm with a maximum aperture of f/4 and you’ll find there’s a saving to be made over a 24-70mm f/2.8. What you save in cost and gain in having a bit more reach at the long end you lose in terms of maximum aperture though. If you’re after a versatile zoom that performs as well in low light as it does creating a shallow depth of field wide open, a pro-spec 24-70mm f/2.8 is the way to go.
The Sigma 24-70mm f/2.8 DG OS HSM Art replaces the ten-year- old Sigma 24-70mm f/2.8 EX DG HSM and is a more affordable alternative to the Canon EF 24-70mm f/2.8L II USM (£1,739), Nikon AF-S 24-70mm f/2.8E ED VR (£2,099) and Sony FE 2470mm f/2.8 G Master (£1,849). It’s a lens we’ve been intending to review since its arrival earlier this year, but how good is it? And should users looking for one of the finest-performing standard zoom lenses consider it?
We’re looking at a lens that’s designed as a go-to for different photographic applications. To maximise its appeal with a wide range of users it has an optical design that’s optimised for DSLRs and mirrorless cameras boasting a resolution of up to 50 million pixels. The lens construction consists of 19 elements in 14 groups with 9 rounded aperture blades. As part of this design, three special low dispersion (SLD) glass elements and four aspherical elements are used to curtail optical aberrations. To keep flare and ghosting under control the front element benefits from Sigma’s Super Multi- Layer Coating that also contributes to sharp, high- contrast images in backlit conditions. Nikon users will find that the lens also incorporates an electromagnetic diaphragm mechanism that allows it to receive the appropriate signals from the camera body for a reliable auto- exposure performance during continuous shooting.
Sigma has once again used its hypersonic motor (HSM) to keep focusing fast and quiet, but this has been refined since previous versions to deliver 1.3x more torque and
provide a more stable performance across its 37cm-infinity focus distance range. Unlike the Canon EF 24-70mm f/2.8L II USM, this Sigma zoom features an optical stabiliser that allows you to shoot four stops slower than would otherwise be possible; however this doesn’t trump another of its close rivals – the Tamron 24-70mm f/2.8 Di VC USD G2 (£1,249), which has the highest vibration compensation level of its class and is effective to five stops. Other noteworthy features include full-time manual focus, which allows the lens to be switched to manual focus simply by rotating the focus ring, an 82mm filter thread, and full compatibility with Sigma’s USB dock to update firmware and adjust focusing parameters using the company’s Optimization Pro software. As things stand the lens is available in Canon, Nikon and Sigma mounts, but isn’t currently available in Sony E-mount. Anyone wishing to pair a Canon or Sigma mount version of this lens with a Sony A7-series camera will want to use Sigma’s MC-11 adapter (£199).
Build and handling
The lens has a practical design. At a glance, it could easily be mistaken for the manufacturer’s 24-105mm f/4 DG OS HSM, but in terms of size it’s fractionally thinner and slightly stubbier. Some will be disappointed to read that it’s not a weather-sealed optic, but the barrel feels strong and robust which should see it stand up to the challenging shooting environments that serious photographers encounter. The barrel contains a large amount of metal in its construction and external moving parts feature thermally stable composite (TSC), which is resistant to thermal expansion and contraction. At the rear a rubber ring compresses against the camera mount to form an effective seal against dust and moisture. The front element also features a water- and oil-repellent coating that allows it to be wiped clean easily.
In terms of weight it’s heavier than its Canon, Tamron and Sony rivals, but is 50g lighter than Nikon’s offering. As with most lenses that weigh over 1kg, it handles best with cameras that offer a large, comfortable handgrip and it didn’t show any sign of zoom creep, which is important, as it doesn’t have a zoom lock. A fairly thin manual focus ring is positioned in front of the focus distance window. Ahead of this is the zoom ring that has its focal length markings printed towards the front. Both the zoom and focus rings are rubberised and it’s easy enough to decipher which is which from behind the camera. The feedback of both rings on our review sample couldn’t be better. The manual focus ring provides sufficient resistance for precise focusing adjustments and the zoom ring operates consistently smoothly and needs very little effort to extend it to its maximum reach. There are two switches on the side of the barrel. Setting the AF/MF switch to its central position engages manual override (MO) and the optical stabilisation is simply set to either on or off using the switch below.
One of the benefits of choosing a standard zoom with a constant aperture of f/2.8 ahead of an f/4 version is the way it permits the use of faster shutter speeds in low light. The
‘ The zoom ring operates consistently smoothly’
opening image to this review is a good example and by shooting wide open at f/2.8 I was able to keep the sensitivity below ISO 1000 while maintaining a 1/60sec shutter speed in order to keep the subject sharp and the image absent of handshake – aided by the effective optical stabilisation, I should add. Our Image Engineering tests, which are carried out at each aperture setting at three focal lengths, revealed a spike in centre sharpness when the lens is stopped down from f/2.8 to f/4, with high sharpness fi gures being returned between f/5.6 and f/8. Corner sharpness is better at wider focal lengths than at the long end and improves gradually as it’s stopped down to f/5.6-f/8. While the sharpest results are obtained by stopping down, shooting at f/2.8 creates some very satisfying images. As my sample images that support this review illustrate, opening the lens to f/2.8 is useful when you want to emphasise a subject from a busy background or surroundings and create a pleasing bokeh in out- of-focus areas.
Vignetting is prominent at the wide end of the zoom at f/2.8, where corners appear approximately 1.4EV darker than the centre. Corner shading is less obvious at f/4 and by stopping down to f/5.6 it vanishes almost completely. The lens is supported by Adobe so if you find yourself shooting at wide apertures and would like to remove vignetting later during post-processing you can select the Enable Profile Corrections option from within Lightroom or Photoshop and it’ll automatically and effectively correct the image for you. The same can be said for correcting distortion. Leave the image untouched and you’ll be aware of barrel distortion at 24mm, which diminishes as you zoom in towards 50mm. Mild pincushion distortion also appears as you encroach 70mm. This level of distortion isn’t a major concern however. It’s easily fixed and is common with most standard zoom lenses that cover a similar focal length.
An example of centre sharpness wide open at the far end of the zoom Canon EOS 5DS R, 1/400sec at f/2.8, ISO 200