In summary
Sigma’s website suggests this lens is suitable for a wide variety of situations, including travel, portraiture, wedding and events and general family photography. We’d add reportage and photojournalism to that list. Its fast maximum aperture across the entire zoom range makes it ideal for low-light work and situations where a narrow depth of field is required.
Potential purchasers should be warned, however, that such a fast lens must, of necessity, contain a substantial amount of glass. This makes the lens large and heavy when compared with lenses that cover similar zoom ranges but are slower.
The constant, fast f/1.8 maximum aperture alone would make this lens a stand-out product. However, when you include its superior build quality and imaging performance it’s clear that Sigma has a winner in the 18-35mm f/1.8 Art lens ““ even without taking its affordable price into consideration.
With its wide-to-normal angle-of-view coverage, this lens is likely to find a place in the kits of many photographers with cropped-sensor cameras. We hope Sigma brings out more lenses in this category and expands the range of lenses available for these cameras because there are significant gaps in some manufacturers’ line-ups.
Full review
When it was announced roughly a year ago, Sigma’s 18-35mm f/1.8 DC HSM Art lens was the first of its type with a constant f/1.8 maximum aperture. Designed exclusively for cameras with APS-C sized sensors, it covers the 35mm equivalent of 29-56mm on Canon DSLRs and 27-52mm on other bodies. It’s currently available with mounts for Canon, Nikon, Pentax, Sigma and Sony DSLR cameras.
The Sigma 18-35mm f/1.8 DC HSM Art lens, shown with the lens hood attached. (Source: Sigma.)
The optical design (shown below) consists of 17 elements in 12 groups and includes a large glass-moulded aspherical lens (one of four aspherical elements) plus five elements made from Special Low Dispersion (SLD) glass to compensate for aberrations and curvature at the widest angle. A Super Multi-Layer coating is applied to minimise ghosting and flare.
The diagram above shows the positions of the exotic glass elements in the Sigma 18-35mm f/1.8 DC HSM Art lens. (Source: Sigma.)
Both focusing and zooming are internal so the lens remains at the same length, regardless of focal length, and the front element doesn’t rotate when you change focus or zoom position. This enables angle-critical filters, such as polarisers, to be used without requiring re-adjustment.
Autofocusing is driven by a ring-type Hyper Sonic Motor (HSM) which uses ultrasonic vibrations to move the lens elements. Manual focus can be used at any time by simply turning the focus ring. Focusing is fast, accurate and almost silent and the minimum focusing distance of 30 cm matches or betters potential rivals.
There’s no built-in stabilisation and it probably isn’t needed for the supported focal length range. In addition, the fast f/1.8 maximum aperture admits enough light to allow the use of shutter speeds more than twice as fast as a typical kit zoom lens supports.
The lens is supplied with a petal-shaped hood plus front and end caps. It accepts 72 mm filters and its iris diaphragm has nine rounded blades, which create a circular aperture to ensure attractive bokeh, an important feature for a fast lens.
Who’s it For?
Sigma’s website suggests this lens is suitable for a wide variety of situations, including travel, portraiture, wedding and events and general family photography. We’d add reportage and photojournalism to that list. Its fast maximum aperture across the entire zoom range makes it ideal for low-light work and situations where a narrow depth of field is required.
Potential purchasers should be warned, however, that such a fast lens must, of necessity, contain a substantial amount of glass. This makes the lens large and heavy when compared with lenses that cover similar zoom ranges but are slower. The table below compares key specifications for the Sigma lens with their fastest close equivalents from the leading DSLR manufacturers.
| Brand | Focal length range | Max. Aperture | Dimensions (Diameter x Length) | Weight | Street price |
| Sigma | 18-35mm | f/1.8 (constant) | 78 x 121.0 mm | 811 grams | $780-$800 |
| Canon | 16-35mm | f/2.8 (constant) | 88.5 x 111.6 mm | 635 grams | $1730 -$1900 |
| Nikon | 17-35mm | f/2.8 (constant) | 82.5 x 106 mm | 745 grams | $2180- $2500 |
| Pentax | 16-50mm | f/2.8 (constant) | 84 x 98.5mm | 565 grams | $1100 – $1540 |
| Sony | 16-35mm | f/2.8 (constant) | 83 x 114 | 900 grams | $2200- $2349 |
As you can see, there’s no competition when it comes to either lens speed or pricing. Whichever way you look at it, the Sigma lens appears to be a genuine bargain.
Build and Ergonomics
The barrel of the lens is made from a new thermally stable composite (TSC) plastic that combines superior hardness with high resistance to thermal shrinkage. This means it’s less likely to slip out of focus as a result of expansion and contraction in changing temperatures.
It also offers 25% greater elasticity than polycarbonate and integrates well with the metal parts, including the chromed brass mount. TSC also enables parts like zoom rings and scaling rings to be made slimmer than other plastics.
The lens itself feels very solid and well-designed and manufactured. It fitted firmly to the mounting plate of the Canon EOS 7D camera we used for our Imatest testing and also to the much lighter EOS 1100D body we used for some of our shooting tests. Interestingly, it felt equally comfortable on both camera bodies, which says a lot for its overall design.
The only thing missing was a rubber gasket to exclude dust and grit. This means the lens can’t be classified as ‘weatherproof’.
The focusing ring is 35mm wide and located 10 mm back from the front of the lens. A 25mm wide strip on this ring is clad with a finely-ribbed rubberised grip band. The ring turns through approximately 160 degrees as you move from the closest focus (28 cm) to infinity. The ring moves very smoothly and there are stops at each end of the range.
A distance scale is inset into the lens barrel behind the focusing ring. It’s calibrated in metres and feet but not as easy to read as it should be because the numbers are small and printed in grey ink. (The feet numbers are harder to read than the metres as they’re darker and tucked half way under the edge of the window.)
Around the barrel to the left of the distance scale is a single slider switch for moving between auto and manual focusing. Sigma has added a nice band of fine ribbing on the underside of the area between the focus and zoom rings, which provides greater comfort when cradling the lens barrel with your left hand.
Between this section and the mount lies the zoom ring, which is about 30 mm wide and partially clad with a 20 mm wide ribbed rubberised grip band. The zoom ring turns smoothly through approximately 70 degrees as you span the focal length range.
The leading edge of the ring is stamped with the following focal lengths, ranging from left to right: 35mm, 28mm, 24mm, 29mm and 18mm. These marks are lined up against a white mark on the non-moving section of the barrel.
There’s a 15 mm wide section of the barrel behind the zoom ring that leads gently in to the mount. The only thing on this section is a white indicator dot for aligning the lens with the camera’s mounting plate.
Performance
Subjective assessments of test shots showed the review lens was capable of producing very sharp images with natural-looking colours and a good distribution of tonal values, regardless of which camera body we used it on. Our Imatest tests were conducted with the lens on a Canon EOS 7D body, this being the camera we thought would best test its capabilities. This camera-plus-lens combination turned in an impressive performance.
While our tests showed the ‘sweet spot’ for sharpness to be around f/4, overall sharpness was very good, even at f/1.8 and diffraction limiting was minimal at f/16. There was also much less variation in performance at different focal lengths than we’re accustomed to seeing with most zoom lenses, as shown in the graph of our Imatest results below.
Lateral chromatic aberration was well controlled and remained within the negligible band at all aperture and focal length settings. In the graph of our Imatest results, below, the red line separates negligible and low CA.
Vignetting was also well controlled for such a fast lens, although some corner darkening can be seen at all focal lengths with aperture settings between f/1.8 and about f/3.2, after which it becomes unnoticeable. Rectilinear distortion was also low for a wide angle lens. There’s a small amount of barrel distortion at 18mm and 20mm and slight pincushioning at 35mm but neither is enough to worry most potential users of this lens.
Although modern cameras include corrections for both these aberrations, they may not be able to ‘read’ the required data from the Sigma lens. However, these aberrations are easily corrected with editing software so neither is a serious problem.
Autofocusing was very fast and very quiet, thanks to the Hyper Sonic Motor, which makes this lens ideal for photographers who enjoy recording movies. Even in low light levels, the review lens locked on quickly and accurately and showed no tendency to hunt for focus. Tracking focus was also satisfactory when shooting moving subjects.
It was difficult to force the review lens to flare when it was pointed towards a bright light source, although we were able to record some artefacts when the sun was inside the frame. However, no loss of contrast was detected in either this shot or in strongly backlit shots and we found no signs of internal reflection patterns with the backlit subjects.
With a minimum focusing distance of 28 cm, this lens isn’t suitable for macro work. But it can be used for shooting close-ups of larger flowers and insects. The constant wide maximum aperture and circular aperture created by the nine-bladed iris diaphragm produce attractive bokeh with very smooth blurring and no distracting tonal transitions.
As part of Sigma’s Global Vision design, this lens is compatible with the new Sigma USB dock and software, which enables users to customise AF microadjustments to suit their personal preferences. Sigma’s MSRP for this product is US$79; it’s selling in Australia for around AU$85).
Conclusion
The constant, fast f/1.8 maximum aperture alone would make this lens a stand-out product. However, when you include its superior build quality and imaging performance it’s clear that Sigma has a winner in the 18-35mm f/1.8 Art lens ““ even without taking its affordable price into consideration.
With its wide-to-normal angle-of-view coverage, this lens is likely to find a place in the kits of many photographers with cropped-sensor cameras. We hope Sigma brings out more lenses in this category and expands the range of lenses available for these cameras because there are significant gaps in some manufacturers’ line-ups.
SPECS
Picture angle: 76.5 to 44.2 degrees
Minimum aperture: f/16
Lens construction: 17 elements in 12 groups (including SLD and aspherical lens elements)
Lens mounts: Canon, Nikon, Pentax, Sigma, Sony
Diaphragm Blades: 9 (circular aperture)
Focus drive: Internal, with Hyper-Sonic Motor; AF/MF switch
Stabilisation: No
Minimum focus: 28 cm
Maximum magnification: 1:4.3
Filter size: 72 mm
Dimensions (Diameter x L): 78 x 121.0 mm
Weight: 811 grams
Standard Accessories: Lens hood, end caps
TESTS
Based on JPEG files taken with the Canon EOS 7D camera body.
SAMPLES
Vignetting at 18mm, f/1.8.
Vignetting at 35mm, f/1.8.
Rectilinear distortion at 18mm.
Rectilinear distortion at 35mm.
18mm focal length, ISO 100, 1/500 second at f/11.
20mm focal length, ISO 100, 1/500 second at f/11.
24mm focal length, ISO 100, 1/500 second at f/11.
28mm focal length, ISO 100, 1/640 second at f/11.
35mm focal length, ISO 100, 1/640 second at f/11.
Close-up at 18mm; ISO 100, 1/500 second at f/1.8.
Close-up at 35mm; ISO 100, 1/500 second at f/1.8.
Flare artefacts recorded when a bright light source was inside the frame; ISO 100, 1/640 second at f/3.5.
Strong backlighting at 18mm; ISO 100, 1/250 second at f/11.
Strong backlighting at 35mm; ISO 100, 1/400 second at f/8.
20mm focal length, ISO 100, 1/500 second at f/11.
35mm focal length, ISO 100, 1/500 second at f/8.
35mm focal length, ISO 100, 1/160 second at f/5.
18mm focal length, ISO 100, 1/320 second at f/14.
35mm focal length, ISO 100, 1/100 second at f/4.
18mm focal length, ISO 100, 1/160 second at f/5.6.
18mm focal length, ISO 100, 1/200 second at f/7.1.
Rating
RRP: AU$899; US$799 (MSRP $1160)
- Build: 8.8
- Handling: 9.0
- Image quality: 9.0
- Versatility: 8.8