Sigma is back with its second 24mm I Series lens this year, the 24mm F2 DG DN Contemporary ($639). It joins the 24mm F3.5 DG DN Contemporary ($549) in the lineup as an alternative for photographers who need better low-light capabilities. We like its high-grade design and sharp optics, even if it doesn’t focus as closely as the 24mm F3.5 and lacks extensive weather sealing. Sony's premium and more durable FE 24mm F1.4 GM ($1,399.99) remains the 24mm to beat for the E-Mount and L-Mount cameras, but the Sigma 24mm F2’s performance makes it a worthy (and much more affordable) contender, earning our Editors' Choice award along with those other two lenses.

I Series Design Ethos

The 24mm F2 DG DN Contemporary is part of Sigma's I Series, a line of camera lenses similar in concept, including aluminum construction, an emphasis on slim and light design, on-lens aperture control, and clever magnetic lens caps. Lenses in the lineup look and feel like vintage glass, but don't sacrifice the modern convenience of autofocus or 21st century optics.

Sigma offers two versions of the lens, one for Sony E-mount cameras and a second for L-mount models from Leica, Panasonic, and Sigma. We had the opportunity to try both; aside from camera compatibility, they're identical.

The 24mm F2 measures about 2.8 by 2.8 inches (HD), weighs 12.9 ounces, and supports 62mm threaded filters. It's bigger than the 24mm F3.5 DG DN Contemporary (1.9 by 2.5 inches, 7.9 ounces, and 55mm filter thread), but by no means huge. Aside from a metal hood, you also get Sigma's classy magnetic lens cap, a standard pinch-cap, and a rear cap in the box.

For L-mount users, the 24mm F2 competes with the Sigma 24mm F3.5 and the Panasonic Lumix S 24mm F1.8 ($900). We haven't reviewed the Lumix, but it sports a more modern finish, uses polycarbonate instead of aluminum, and offers full dust and splash protection. The Sigma 24mm F2 (and F3.5 for that matter) include a seal only at the lens mount, so they aren't fully weatherproof.

Sony photographers have additional options. The FE 24mm F1.4 GM is, bar none, the best 24mm I've used. But at $1,400, it's out of budget for many. Sony also offers the lightweight 24mm F2.8 G ($600). The Tamron 24mm F2.8 is worth a look too if you're a thrifty photographer—it sells for around $200.

Tactile Controls Make a Difference

The 24mm lens doesn't just look sharp—it feels premium in the hand, too. The aperture ring turns with a gentle nudge and locks into place at third-stop settings from f/2 down to f/22. There's also an A setting that, when you enable it, moves f-stop control to the camera body. I like using the ring; it brings a bit of analog handling to the digital world. Besides, it's easy enough to move control to the camera body—not a bad idea if you shoot video because the clicking ring can introduce noise to the soundtrack.

Focus breathing, the effect in which the angle of view changes with focus, is evident. There's a modest zoom-out effect when shifting focus from near to distant subjects. It makes the lens a less-than-great pick for rack shots that shift focus between subjects.

Instead of focusing on video, the lens puts the wants of photographers first—manual focus response is nonlinear, so turning it quickly makes more aggressive changes to focus than turning it slowly. For video, a linear response is preferable, one based on how far, not how quickly, you turn the ring—this behavior makes it easier to repeat focus shifts.

On the plus side, autofocus is very quiet and responsive. The lens is quick to change focus modes, and the 24mm's lone toggle switch lets you swap between manual and automatic controls. Close focus distance is the same in either case (about 9.7 inches) and nets a non-macro 1:6.7 magnification. The 24mm F3.5 Contemporary focuses closer (4.3 inches) for 1:2 macro results.

24mm F2 DG DN Contemporary: In the Lab

I paired the 24mm F2 with the 60MP Sony a7R IV to check its resolution. Imatest's SFRplus evaluation shows it to be a strong performer. At f/2 it nets excellent scores (4,600 lines). It improves steadily as you narrow the aperture, and falls just shy of outstanding results (5,000 lines) at f/4 and f/5.6.

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Resolution holds steady down through f/11. Optical diffraction, an unavoidable effect of light passing through a narrow iris, softens results a little at f/16 and noticeably so at the smallest f/22 setting. You may still want to use these f-stops though—the lens draws its best sunstars when stopped all the way down.

At wide apertures, the 24mm F2 produces photos with a shallow depth of field, the blurred-background look that sets full-frame cameras apart. The quality is in line with other modern lenses and emphasizes smooth, soft blur. Highlights are circular toward the center, but show a distinct cat's eye shape toward edges and corners at f/2. Stopping down to f/2.8 rounds out the highlights across the frame.

In-camera corrections are available for JPG and HEIF photography. They automatically compensate for some defects visible in unprocessed Raw images—barrel distortion, as well as a vignette that's visible at f/2. Adobe includes a profile for the lens in the latest Lightroom Classic release and applies it automatically on import. If your Raw processor doesn't have a profile for the lens, the barrel distortion isn't too much to take care of manually—in Lightroom, a +20 Distortion adjustment does the trick.

Sigma I Series Continues to Impress

We've been happy with the Sigma I series lenses thus far. Aluminum construction and on-lens aperture controls set them apart from lenses with less inspired designs.

The 24mm F2 joins the 24mm F3.5 Contemporary in the I Series family. The two lenses look and feel similar, although the smaller F3.5 is better for close-up work. The 24mm F2 is slightly bigger, but it gathers more light and is a better fit for low-light scenes—think night sky photography and architectural interiors.

Both Sigma 24mm lenses are strong contenders for a spot in your camera bag. Which you should buy depends on your photographic style. Therefore, we're giving both of them the same four-star rating and Editors' Choice designation. If you frequently work in dim light, the 24mm F2 offers a much better value than the expensive Sony FE 24mm F1.4 GM and undercuts the Panasonic Lumix S 24mm F1.8 on price as well.

All that said, the $1,400 Sony FE 24mm F1.4 GM remains top of the pack in this focal length. If you have the money, its brighter f-stop and all-weather construction justify its premium. But the rest of us, especially photographers working on a budget, can get by just fine with the Sigma 24mm F2 DG DN Contemporary.