The third generation of Sigma’s 12-24mm lens joins the company’s ‘Global Vision’ lineup, bearing an Art designation – this is reserved for Sigma’s lenses that are engineered to deliver optimum optical performance while maximizing artistic expression. Along with Sigma’s 8-16mm for APS-C format cameras, the fullframe- compatible 12-24mm II used to boast the widest viewing angle of any rectilinear zoom lens on the market, at 122 degrees. Canon overtook it with the launch of the 126-degree EF 11-24mm, a seriously professional lens at a monstrously expensive £2700/$3000. The new Sigma Art lens is only about half the price of the Canon, yet boasts some significant enhancements over its Mk II predecessor.
Like the Canon lens, the new Sigma moves to a constant rather than variable aperture design, rated at f/4 instead of f/4.5-5.6. There’s an extra top-grade FLD (Fluorite-level Low Dispersion) element, bringing the total count to five, along with one SLD (Special Low Dispersion) element. Of the two aspherical elements featured, the front one has a diameter of 80mm, making it the largest in any ultra-wide zoom on the market.
Further enhancements over the Mk II lens include water- and oil-repellent fluorine coatings on the front and rear elements, and a weather-sealed mounting plate. The ring-type ultrasonic autofocus system has been redesigned to give more torque, and the new lens gains compatibility with Sigma’s USB Dock for customizing settings and applying firmware updates.
The 12-24mm certainly isn’t little or lightweight at 102x132mm and 1150g, but it’s still marginally smaller and lighter than the Canon 11-24mm. Handling is excellent. The zoom and focus rings have a smooth and fluid feel while offering high-precision adjustments. As usual with an ultra-wide lens, the hood is a permanent fixture that forms an integral part of the barrel.

Performance
True to Sigma’s claims, autofocus speed is very quick and practically snaps into position. There’s very good sharpness and contrast throughout the zoom range, even wide open at f/4. Corner sharpness in particular is noticeably improved from the Mk II lens. Colour fringing is much reduced and distortions are far less noticeable. That said, distortion scores certainly aren’t perfect in our lab test results, based on very close-range shooting of test charts. However, in landscape and architectural photography, as well as when shooting interiors of buildings, distortions are generally, and pleasingly, negligible.
When shooting at or near the minimum focus distance of 24cm, the lens is capable of exaggerating perspective with incredible effect, while the f/4 aperture enables you to blur the background to some extent, despite the short focal length range. Resistance to ghosting and flare is very good indeed. Overall, the new Sigma Art lens is excellent in all aspects of performance.

Full-Frame compatible Yes
eFFective Focal length 12-24mm full-frame, 19.2-38.4mm APS-C
image Stabilizer No
minimum FocuS diStance 0.24m
max magniFication Factor 0.2x
manual FocuS override Yes
FocuS limit SwitcheS No
internal zoom Yes
internal FocuS Yes
Filter Size N/A
iriS bladeS 9
weather SealS Partial
Supplied acceSSorieS Soft case
dimenSionS (dia x length) 102x132mm
weight 1150g
price £1650/$1600