The Sigma 18-35mm f/1.8 DC HSM is the worldu2019s first zoom lens with an f/1.8 maximum aperture, but itu2019s not as expensive as you might think. Richard Sibley and Andrew Sydenham compare the lens with the Canonu2019s premium EF 16-35mm f/2.8L II and find out how good it is
Image: Sigma 18-35mm f/1.8 DC HSM
One of the first things that strikes you as you pick up the Sigma 18-35mm lens is its weight. Although it is designed for the smaller APS-C-sized sensor, the large f/1.8 aperture means that some fairly significant size glass lens elements have gone into its construction.
With 17 elements in 12 groups it is no surprise that the 18-35mm lens weighs a hefty 810g. To put this in perspective, the Canon 24-70mm f/2.8L II USM lens is 5g less at 805g, and the Canon EF 16-35mm f/2.8 II USM lens that we are using as a comparison weighs just 640g. While around 110g difference may not seem a huge amount, the weight becomes more significant the longer you are carrying the lens, especially as it is likely to be used for landscapes and travel photography so it may be on your shoulder for an entire day.
As you would expect from a lens with 17 elements, the design of the Sigma 18-35mm f/1.8 lens is extremely complex. Four of the elements are aspherical and five are made from Special Low Dispersion (SLD) glass. The combination of both these types of elements helps control chromatic aberrations and curvilinear distortions. To reduce flare and ghosting, and to maximise contrast and sharpness, the lens elements also feature a Super Multi-Layer coating. Extra protection from flare is also provided by using the supplied petal-shaped lens hood. When focusing the lens the front element does not move, which is useful for those shooting landscape images and wishing to use a circular polarising filter. The lens has a 72mm filter thread.
The aperture of the Sigma 18-35mm f/1.8 lens features nine rounded blades. This helps create completely circular and smooth specular highlights, producing an attractive bokeh, which is an important feature given the very shallow depth of field that can be created with the f/1.8 maximum aperture.
Image: Canon EF 16-35mm f/2.8L II
With a minimum focusing distance of 28cm, the Sigma 18-35mm allows photographers to get relatively close to their subjects and, of course, when shooting at f/1.8 the minimum focus distance provides a very shallow depth of field. The lens uses a Hyper Sonic Motor (HSM), and this ensures that focusing is both fast and as quiet as possible. Switching between manual focus and autofocus can be done via a switch situated on the side of the lens barrel.
The lens is largely constructed of metal, including a brass lens mount. Overall, the Sigma lens is built to an extremely high standard. Third-party lenses are often seen as inferior to manufacturers’ own lenses, but this is certainly not the case with the Sigma 18-35mm f/1.8. The new design, with its large, easy-to-use focus and zoom rings, looks as good as it is to use, and denoting the year in which the lens was designed is a really nice touch. For example, the Sigma 18-35mm f/1.8 is marked 013, while a version released in 2017 would state 017, rather than the Mark II that other manufacturers do. I like this idea and can see people discussing certain generations of the lens in the future – along the lines of, say, ‘I always prefer the 014 version to the latest 022 as there is slightly less curvilinear distortion.’ Overall, the lens is certainly as well constructed as the Canon 16-35mm f/2.8 lens and I think that, if anything, the Sigma lens feels nicer to use.
One of the advantages of Sigma’s new lenses is that they can be used with the company’s USB dock, which allows compatible lenses, such as the 18-35mm f/1.8, to be connected via the dock to a computer. Using software supplied with the USB, dock lenses can have their firmware updated and it is even possible to correct for and adjust slight front or back focusing inaccuracies. Some telephoto lenses can even have custom minimum and maximum focus distance set, although this obviously doesn’t apply to the Sigma 18-35mm f/1.8 lens.