This full-frame, ultra-wide-angle prime for mirrorless cameras is perfect for night sky photography, landscapes, interiors, weddings, travel and architecture. Its ultra-wide aperture of F1.4 ensures very fast shutter speeds in lower light conditions, as well as a very shallow depth-of-field for pronounced subject separation.
The lens comes with a raft of pro-level features that includes an aperture ring with de-click and lock switches, an AFL button, a lockable lens hood, a rear filter holder, a Lens Heater Retainer and a manual focus lock feature. The optical design includes two SLD and three aspherical elements, one of which is the largest double-sided aspherical glass element in Sigma’s history. These advanced optics ensure very minimal chromatic aberration, sagittal coma flare and image distortion, giving highly-detailed images with exceptional sharpness and accuracy from the centre to the periphery of the frame.
The exceptional build quality of the 20mm F1.4 DG DN is exactly as you’d expect from an Art-line lens, both in the materials used, the overall ergonomics and the quality of craftsmanship.
The exterior barrel is made of a polycarbonate called Thermally Stable Composite (TSC). Not only is this very strong and light, but it has a similar thermal expansion rate to aluminium. This ensures that the interior aluminium parts and the exterior TSC parts behave in the same way as temperatures change.
The focus ring is rubberised for easier operation, and focusing is internal, meaning the lens never changes length. This makes it ideal for use on a gimbal as the centre of gravity remains fairly constant.
Towards the rear of the barrel is an aperture ring, which can be de-clicked for stepless aperture changes. When put into Auto, aperture is controlled by the camera. A lock switch allows users to lock the ring in Auto or Manual so it’s not accidentally knocked into a different setting
To reduce flare and ghosting in bright sun, and to help protect the front element from damage if dropped, the lens has a robust petal-type lens hood with lock button. A rubberised ring on the hood makes for easier removal and fitting.
The durable brass mount is surrounded by a rubber seal to help keep out dust and moisture.
Precision brass mount with seal
Protects against dust and moisture.
Made from a strong and light polycarbonate that behaves in a similar way to aluminium.
Focus Mode switch
For changing between AF and MF.
Customisable depending on camera body.
Manual Focus Lock switch
Completely disengages the focus ring for locking focus.
Aperture Click switch
Clicks or de-clicks the aperture ring.
A range of controls on the lens include an AF/MF switch, a customisable AFL switch and switches to de-click and lock the aperture ring.
The lens also has a Manual Focus Lock switch that allows users to completely deactivate the focus ring once focus has been acquired, ensuring that focus won’t change should the ring be accidentally knocked.
The 20mm F1.4 has an 82mm filter thread at the front of the lens, as well as a filter holder at the rear. The rear filters (available from several filter manufacturers) are about the size of an SD card, so very small and light, and as they’re positioned between the camera and lens, don’t tend to get damaged or dirty. It’s easy to cut filters by hand from gel sheets as a special template is included with the lens.
The 20mm F1.4 DG DN | Art delivers outstanding optical quality, with excellent rendering of detail right into the corners even wide open at F1.4.
The lens has an advanced optical design made up of 17 elements in 15 groups, including 3 aspherical elements and 2 SLD elements. This ensures razor-sharp results and helps to eliminate chromatic aberration, flare, distortion and vignetting.
Advanced optical coatings reduce flare and ghosting when working in bright direct sunlight, creating high-contrast images with rich colours and strong blacks.
Having an F1.4 aperture and therefore a very shallow depth-of-field makes this lens ideal for environmental portraits, where a subject is portrayed in context with their surroundings.
The shallow depth-of-field helps the subject stand out from the background.
With a magnification ratio of 1:6.1, the 20mm can shoot relatively close-up for an ultra-wide-angle lens. This equates to a minimum focusing distance (subject to sensor) of 23cm, which puts the subject about 12cm from the end of the lens. This, combined with a shallow depth-of-field, makes for attractive close-up images.
SIGMA’s two wide-angle F1.4 DG DN primes – the 20mm and 24mm – are extremely similar in design and spec. Both have aperture rings with lock/de-click functions, both have MFL and AFL buttons, and both have similar petal-type lens hoods with lock buttons. Both lenses also have rear filter holders, although on the 24mm, glass filters can be used, whereas they can’t on the 20mm due to a slightly different design. The 20mm has the Lens Heater Retainer lip, whereas the 24mm doesn’t.
All Sigma cameras and lenses are designed, manufactured and assembled at our sole factory at Aizu in Japan. This domestic production model is unusual in today’s industry, with most imaging companies opting to outsource to other countries to reduce costs. But SIGMA believes that keeping virtually all manufacturing, processing and assembly in Aizu is essential for creating innovative, carefully thought-out and impeccably constructed products that meet the high standards demanded by professional photographers and film-makers around the world.
Sigma chose Aizu as its main production base in the early 1970s. Situated at the base of Mount Bandai in the Fukushima Prefecture, about four hours’ drive north of Tokyo, Aizu has an abundance of very clean water from mountain streams, which is essential for grinding and polishing lenses. Sigma’s founder, Michihiro Yamaki, was also drawn to this area for its workforce, who have a reputation for their craftsmanship, work ethic and attention to detail. Mr Yamaki’s son, Kazuto Yamaki, now the owner and CEO of SIGMA Corporation, has the same unwavering commitment to keeping production in Japan.
Today Sigma’s factory is more than 50,000 square feet in size, and packed full of some of the most advanced optical manufacturing technology in existence. So when you buy a Sigma camera or lens you can be sure that virtually every single component part has been manufactured and assembled by SIGMA, in Japan, with the greatest level of care and attention. We hope you enjoy using our products.
If you want to see how a particular SIGMA lens or camera performs, why not test drive it with our SIGMA Select hire service. Available for selected SIGMA lenses, short-term loans are free of charge (including shipping), with a small fee if you want to test it for longer. Refundable deposit required. Subject to availability.
17 elements in 15 groups
Angle of view
Number of diaphragm blades
11 (rounded diaphragm)
Minimum focusing distance
Maximum magnification ratio
Dimensions (diameter x length)
ø87.8mm × 111.2mm
Corresponding AF mounts
L-Mount | Sony E
Sony E barcode
Specifications are for L-Mount
A special coating applied to the front element to help repel water and oil.
This suppresses flare and ghosting by minimising reflections within the lens, ensuring punchy, high-contrast results. All lenses in the current Sigma range feature this technology.
This allows filters to be added at the rear of the lens. The filters are about the size of an SD card, and can be purchased or cut out from a sheet using a special template. Because these filters aren’t open to the elements they stay clean, and are much easier to carry around.
This describes the degree to which a lens can magnify an in-focus subject. The ratio shows the relationship between the size of the projection of a subject on the camera’s sensor (the left number) and its actual size in reality (the right number).
Internal focus or an inner focus system means the lens configuration uses movable internal lens elements that adjust focus without changing the length of the lens barrel. This helps keep the centre of gravity of the lens more constant when changing focus.
The lens has an image circle large enough to be used on a full-frame camera. It can also be used on cameras with a smaller ‘crop’ sensor, provided the mount is compatible.
The lens has a filter thread around the front element onto which filters and filter holders can be attached.
The mount is the part of the lens that attaches to the camera body. A coated brass mount is used for strength, and is surrounded by a rubber seal to keep out dust and moisture.
Found on the barrel of some Sigma lenses, the AFL button can be assigned to various functions to widen the range of operations available on the lens (available functions depend on the camera model).
This switch toggles between autofocus and manual focus.
The diaphragm is constructed of 11 rounded blades for a circular aperture opening and round out-of-focus highlights.
The diaphragm is constructed of nine rounded blades for a circular aperture opening and round out-of-focus highlights.