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Meet the new Sigma 20mm f/2 DG DN prime lens for full-frame mirrorless L- and E-mount cameras. It’s the seventh lens in the brand’s “I” series of lightweight, compact, high-performance primes, and also the widest in the series. I series lenses are part of the brand’s “Contemporary” line.

The new Sigma 20mm will ship on February 25th for $699. Let’s take a closer look.

Who’s it for?

A fast, wide-angle prime is an invaluable piece of kit for a range of photographic disciplines. In particular, we could see this appealing to astrophotographers, landscape shooters, street photographers, interior shooters, and more. It’s also a good fit for anyone working in low light conditions, like wedding, event, and live music photographers.

Additionally, the Sigma 20mm could potentially be a good wide-angle option for video shooters, seeking something rugged and compact. In fact, the L-mount version features an option to toggle manual focus control between linear and nonlinear responses. The former allows for repeatable manual focus pulls. That said, Sigma makes no mention of whether not focus breathing—where the field of view shifts during a focus pull—is well controlled. This is something video shooters will surely want to know before investing.

Nevertheless, Sigma has hinted that this linear/nonlinear functionality will be brought to other I series lenses in the future, via firmware updates. Speaking of firmware, the new Sigma 20mm is compatible with the brand’s USB lens docks.


The new Sigma 20mm f/2 DG DN
The Sigma 20mm ships with a petal-type metal lens hood. Sigma

All of Sigma’s I series primes feature rugged constructions. And the Sigma 20mm is no exception. It’s built from machined aluminum with a brass base and is both dust- and moisture resistant. Even the lens hood is metal.

As mentioned, the footprint of this lens is pleasantly compact, it weighs just 13.1 ounces and is 2.8-inches wide and 2.9-inches long. The lens barrel has a manual focus ring near the front and an aperture ring—with an “auto” position—near the back. There is also an AF/MF toggle on the side of the barrel.

The front accepts 62mm filters and the lens ships with a magnetically-attaching cap.

Optical construction

Optically, the new Sigma 20mm is comprised of 13 elements in 11 groups, with three aspherical elements and two different low-dispersion elements included in the mix. Sigma promises excellent edge-to-edge sharpness, and for astrophotographers, well-controlled coma.

Multiple special coatings should also help to reduce and even eliminate instances of ghosting or lens flare. And an 8.7-inch minimum focus distance doesn’t quite put this into macro territory, but it does mean you’ll be able to get fairly up close and personal to your subjects.

Autofocus and aperture

The new Sigma 20mm f/2 DG DN
In between the aperture and focus ring is an in indentation for resting one’s finger. Sigma

Autofocus power comes from a stepping motor (STM), which should mean ultra-silent, ultra-fast AF acquisitions. Focusing is internal, meaning the lens does not extend/contract as it racks. The Sigma 20mm sports a 9-blade diaphragm, with apertures ranging from f/2 to f/22.

Price and availability

The new Sigma 20mm f/2 DG DN will start shipping at the end of February for an MSRP of $699.