I have wanted to try the Sigma 18-35mm f/1.8mm DC HSM zoom lens ever since it was announced earlier this year. As it is designed for an APS-C-sized sensor, the field of view isn’t quite as wide as you might expect, but it works out as roughly equivalent to a 28-50mm lens, making it useful for landscapes and reportage photography. In fact, with an f/1.8 constant aperture, it could easily replace a 24mm, 28mm and 35mm lens in the kit bag of those with a DSLR carrying an APS-C-sized sensor.

This lens is part of Sigma’s new Art range of lenses, which is the designation given to wideangle, large aperture or macro lenses. Basically, the Art-series lenses are meant to be for creative uses, whereas the Contemporary-series lenses are more for standard uses, while the Sports-series lenses are telephotos designed for sports and wildlife photograph. The aim is to simplify the nomenclature given to lenses, and rightly so, but until we get used to this it may be a little bewildering.

It isn’t just the categories of the lenses that have been given a new lease of life, either, as the actual design has also been revamped and the lenses have been given a stylish, rather minimalist look. Gone are the gold bands that used to feature on Sigma optics. Now they are matt black with simple white labelling, and look perfect alongside today’s retro-styled cameras that are now in vogue.

As a ‘world’s first’, there is obviously no like-for-like competition for the Sigma 18-35mm f/1.8 lens. However, to be able to see how good it is and to draw comparisons, we have chosen to test it alongside the Canon EF 16-35mm f/2.8L II lens.

The Canon optic is around six years old, having been released in early 2007. It is one of Canon’s premium L-series lenses, which is reflected in its price – it is almost £1,200. At this price, the Canon 16-35mm f/2.8 lens is almost twice the price of the Sigma 18-35mm f/1.8, which is around £650, but there is one major difference between the two lenses. The Canon lens is designed for use on cameras with a full, 35mm image frame, while the Sigma lens can only be used on cameras with an APS-C-sized image sensor. Obviously, this means that the 16mm focal length of the Canon lens is even more impressive, as it truly is a 16mm lens when used on a full-frame camera. The difference in the field of view of the Sigma lens means it is the equivalent of a 27mm lens on a camera with a full-frame sensor. For the purposes of this comparison, both optics have been used on an 18-million-pixel Canon EOS 7D, which has an APS-C-sized sensor.

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.

Specification: Sigma 18-35mm f/1.8 DC HSM

RRP: £799.99
Street price: Around £650
Filter diameter: 72mm
Lens elements: 17
Groups: 12
Diaphragm blades: 9
Aperture: f/1.8-16
Minimum focus: 28cm/11in
Length: 121mm
Diameter: 78mm
Weight: 810g
Lens mount: Canon EF, Nikon F, Sigma, Sony A, Pentax K

Sigma 18-35mm f/1.8 DC HSM – 18mm

Chart analysis

Tested on a Canon EOS 7D

Set to f/4 at its 18mm focal length, which is 2 stops down from maximum aperture, the performance of the Sigma 18-35mm lens is extremely sharp. At MTF 50% the resolution is around 1200lp/ph. Like the Canon lens, the Sigma 18-35mm has a slightly wavy vignetting shading graph, probably due to the complexity of all the lens construction being pushed to the limit at this short focal length. However, the actual shading is minimal, with only around 0.1EV difference in exposure.
Looking at the distortion the Sigma lens is almost identical the the Canon lens at this focal length.

Sigma 18-35mm f/1.8 DC HSM – 24mm

Chart analysis

Tested on a Canon EOS 7D

Like the Canon lens, the wave of the vignetting has smoothed out in the Sigma lens. However, there is still around 0.1EV darkening at the very edges.

There is a drop in the amount of detail the lens can resolve with the MTF 50% figure reduced to around 1000lp/ph, which is still better than the performance of the Canon 16-35mm lens. It is worth noting that there is only a slight difference between using the lens at f/1.8 and f/4, as the dark blue and red lines of the graph indicate.

Sigma 18-35mm f/1.8 DC HSM – 35mm

Chart analysis

Tested on a Canon EOS 7D

Like the Canon lens, pincushion distortion of the Sigma lens is present at this focal length, and once again there is fractionally less vignetting than at the 24mm setting. Resolution is still very high and, again, with the lens aperture set to f/1.8 or f/4, the resolution is greater than 1000lp/ph at MTF 50%, which is very impressive. What is even more pleasing is how close all the lines are, showing very little difference between apertures at the centre and edges. This is clearly as a result of the centre areas of the lens being using to create the image at this focal length. Overall, performance is extremely good.

Score: 4 out of 5

Specification: Canon EF 16-35mm f/2.8L II

RRP: £2,147.99
Street price: Around £1,180
Filter diameter: 82mm
Lens elements: 16 elements
Groups: 12
Diaphragm blades: 7
Aperture: f/2.8-22
Minimum focus: 28cm/11in
Length: 111.6mm
Diameter: 88.5mm
Weight: 640g
Lens mount: Canon EF

Canon EF 16-35mm f/2.8L II – 16mm

Chart analysis

Tested on a Canon EOS 7D

At its widest setting the distortion of the Canon 16-35mm lens is around the same as the Sigma 18-35mm lens, and will require some correction. Interestingly there is a slight wave on the vignetting, no doubt caused by the complex lens design, but overall vignetting is virtually non-existent.

Although the chart shows that the lens performs fractionally better when wide open, this wasn’t reflected in our real-life test. There was very little difference between the image resolution at f/2.8 and f/5.6 with the lens performing well at both apertures, although not as well as the Sigma lens.

Canon EF 16-35mm f/2.8L II – 24mm

Chart analysis

Tested on a Canon EOS 7D

With the longer focal length of the Canon lens, the slight wave in the shading graph is smoothed out, and again there is virtually no vignetting.

Resolution is very similar to when the lens is used at the 16mm setting, although the difference between centre and edge resolution at each given aperture is less, which is represented by the lines on the graph being closer together.

The curvilinear distortion is minimal and by the 24mm focal length shouldn’t be an issue.

Canon EF 16-35mm f/2.8L II – 35mm

Chart analysis

Tested on a Canon EOS 7D

At its longest focal length there is some pincushion distortion of the Canon lens, as indicated by the arrows at the bottom of the graph. However, it isn’t too severe and is straightforward to correct. Any vignetting is virtually unnoticeable in real-world images as it is less than 0.1EV. The lens actually seems to be at its sharpest at this setting, managing to resolve at 800lp/ph at MTF 50%. Performance at the edges when the lens is at its maximum f/2.8 aperture is poor and drops to less than 400lp/ph at MTF 50%.

Score: 4 out of 5

Just a quick glance at the resolution charts of the Sigma 18-35mm f/1.8 DC USM reveal that it is a great lens. With an MTF 50% resolution of around 1000lp/ph at f/4, regardless of the focal length, the 18-35mm can actually resolve as much as some of the 50mm lenses we tested previously (see AP 20 July), which is impressive for a relatively wideangle zoom lens.

However, the Sigma is really at its sharpest when shooting at around f/4 at its 18mm setting, which is the equivalent of a 27mm field of view on a full-frame camera. This is good news for those looking for a mid-range zoom lens for landscapes, especially as even at the edges there is only a moderate decrease in sharpness. The only downside is that the minimum aperture is only f/16, rather than f/22. Obviously, landscape photographers will want to maximise depth of field, but thankfully the lens is still acceptably sharp at f/11 and even at f/16 diffraction isn’t so bad that it is unusable.

The images below were taken at the 35mm focal length of each of the lenses. The lenses were focused on the point highlighted, and are shown enlarged.
The Sigma 18-35mm f/1.8 lens resolves fractionally more detail than
the Canon 16-35mm f/2.8 lens, with both lenses at their sharpest between
f/5.6 and f/8

Image: Taken with Sigma 18-35mm f/1.8 DC HSM lens at f/1.8

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/2.8

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/4

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/5.6

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/8

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/11

Images: Taken with Canon 16-35mm f/2.8L II (left) and Sigma 18-35mm f/1.8 DC HSM lens (right) at f/16

Image: Taken with Canon 16-35mm f/2.8L II lens at f/22

Looking at the real-life images above, the differences between the resolution of the lenses are put into a different perspective. There is only a slight difference between the resolving power of the Sigma 18-35mm f/1.8 and the Canon 16-35mm f/2.8 lens. Overall, the Sigma appears slightly sharper in every comparable image, and there also seems to be slightly more contrast in the images taken with the Sigma lens. Of course, the additional contrast is down to the coating on the lens, and when shooting an MTF chart with its many fine converging lines, the extra contrast will help to differentiate the lines, producing better results in the test. So, under test conditions, the Sigma does produce more detailed images, but in real-world results the difference is less noticeable than the results would have us believe.

Vignetting is so minimal across the different focal lengths of the Sigma lens that it should really be of no concern. The Canon 16-35mm has an even better performance, which is most likely due to the fact that it is a full-frame lens being used on a camera with an APS-C-sized sensor.

As expected from two lenses with such complex designs and wide focal lengths, there is quite a bit of curvilinear distortion present at either extreme. At the shortest focal length the distortion will require some correction, either in-camera or when editing raw images. The results of the distortion for both lenses at their widest field of view are remarkably similar, although the Canon lens has the advantage at the 24mm focal length setting and by around 28mm the distortion is almost zeroed. At 35mm, both lenses begin to show pincushion distortion. The pincushion distortion is fairly minimal and with some subjects images it won’t even need correction.

It would be difficult to talk about the Sigma 18-35mm f/1.8 DC HSM without mentioning the performance of the lens at f/1.8. The lens coating and level of contrast mean that the performance is excellent and the lens has a lovely smooth out-of-focus bokeh. Combined with the shallow depth of field produced, the lens is great for taking mid-length portrait images when set to its 35mm focal length, with the aperture throwing any distracting backgrounds nicely out of focus.

Overall, the image quality of the Sigma 18-35mm f/1.8 DC HSM lens is excellent, especially when you consider that it is a world first.

With the new design and branding of its lenses, Sigma is clearly trying to change its image from one of being a third-party lens manufacturer to a company whose products are respected just as highly as a manufacturer’s proprietary lenses. Usually, all this needs is a couple of standout lenses that photographers will want regardless of the camera system they own.

The specification of the Sigma 18-35mm f/1.8 DC HSM lens is certainly enough to raise a few eyebrows, and, as I said at the beginning of this article, I was looking forward to using it ever since it was announced. Thankfully, the lens lived up to my expectations and it is one I hope to get a lot of use out of in the years ahead.

Optically, the Sigma lens is a match for the more expensive Canon EF 16-35mm f/2.8L II USM, with the obvious disclaimer that the Sigma can only be used on cameras with APS-C-sized image sensors. The lens designers at Sigma have done an excellent job, and image quality is matched by the exterior build quality.

There are downsides to the Sigma lens, though. For instance, the complex construction means that it is fairly heavy, and a minimum aperture of f/16 may put off some landscape photographers. However, even at this smallest aperture diffraction seems to have only a minimal effect. I would suggest this is the reason Sigma didn’t try to push the lens to f/22, where it may have become noticeable.

Overall, landscape photographers should enjoy using this Sigma lens, and the f/1.8 aperture should produce some interesting images at the minimum focal length. It will also be a good lens for travel photographers, with the large maximum aperture helping with low-light images. If only the lens were a little lighter it would be hard to find any fault with it. With Nikon and Canon versions available, and Pentax and Sony versions coming soon, the Sigma 18-35mm f/1.8 DC HSM lens will find its way into a lot of photographers’ kit bags this year, especially with its very reasonable street price of around £650.

Image: At the Sigma’s minimum focus distance of f/1.8,
there is a nice shallow depth of field and the circular aperture blades
create smooth, out-of-focus areas