The $149 Sirui Swift 40mm f/2.2 vs. Three Pricier 40mm Primes

At $149, the Sirui Swift 40mm f/2.2 costs less than Sony's, Nikon's, and Viltrox's compact 40mm autofocus primes, and only Nikon's is brighter. If you've been eyeing a small prime as your first step up from a kit lens, the trade-offs at that price turn out to be modest: a little extra weight and some color fringing.

Dustin Abbott puts the Swift 40mm up against three 40mm lenses he has already reviewed: the Sony FE 40mm f/2.5 G, the Viltrox AF 40mm f/2.5, and the Nikon NIKKOR Z 40mm f/2. Each rival has a weak spot in his view. At $798, the Sony is a lot of money for an f/2.5 lens. The $168 Viltrox is very sharp for its price, but its rendering is only so-so, and the Nikon, at about $300, draws softly and pleasantly but isn't especially sharp wide open. His verdict is that the Sirui pulls the best of them together, with the Sony's controls and weather sealing, rendering closer to the Nikon's, and sharpness near the Viltrox's. The Sirui comes in Sony E, Nikon Z, L-mount, and Fujifilm X versions, and Abbott tested it on Sony.

On the outside, little seems to have been sacrificed. You get a clicked aperture ring, a function button, an AF/MF switch, a weather-sealing gasket at the mount, and a USB-C port for firmware updates. Among the competitors, only the Sony has the ring, button, and switch, and the Viltrox has no weather-sealing at all. The cost is weight: at 210 g, the Sirui is the heaviest of the four, though still light enough that you won't notice it on a small body. Inside are nine rounded aperture blades, and the 58mm filter thread takes common, inexpensive filters. Minimum focus is 40 cm for 0.14x magnification, which Abbott calls about average and below what the Sony and Nikon manage.

A 40mm lens sits close to the diagonal of a full frame sensor, which measures about 43mm, and that's what gives the focal length its natural look. Frames come out a bit wider than a 50mm, with perspective that feels close to how your eyes take in a scene, so it works well as a single walk-around lens for street, travel, and casual video where you want some context around your subject without wide-angle stretching at the edges. If you shoot Fujifilm X, keep the crop factor in mind: the X-mount version frames like a 60mm, which nudges it toward tight portraits and details instead of wide scenes.

Autofocus comes from an STM-style stepping motor, and on cheap lenses that can mean hunting or noise. Abbott found it fast, quiet, and accurate, with very little slowdown racking between close and distant subjects and no trouble locking onto backlit scenes or fine lines. He notes that Sony tends to give the best third-party autofocus experience of the systems he tests on, so behavior on other mounts may differ. For video, touch-to-focus pulls land smoothly without visible steps or pulsing. Focus breathing is noticeable, and because this is a third-party lens, Sony's in-camera breathing compensation can't correct it.

The optical design uses 11 elements in eight groups, including one aspherical element, and distortion is essentially nonexistent. Vignetting shows up wide open, and correcting it can leave a faint color shift in the corners, though Abbott rarely felt the need to fix it in real-world shots. The flaw he points to most is chromatic aberration, which appears as blue-green fringing just behind the plane of focus on high-contrast subjects like frost crystals. On the 61-megapixel Sony a7R V, center detail is strong at f/2.2, and the corners hold up better than you'd expect at this price. Stopping down mostly adds contrast instead of resolution, and diffraction begins softening images by f/11 on a sensor that dense.

On his test chart, the Viltrox has a little more contrast wide open and slightly more even sharpness into the corners. In real photos, though, Abbott found the Sirui matched much of the Viltrox's resolution while rendering more nicely, and he rates its bokeh a bit better, too, though backgrounds can turn busy when the subject is farther away. With the sun in or near the frame, it shows some ghosting and veiling, which he says you can work around by composing carefully. Sirui sent the lens for review, and Abbott says the company had no input and wouldn't see the video before it went up. He liked it enough to agree to review the other new Swift lens, a 20mm f/2.4.

If the fringing worries you, the frost crystals Abbott shoots partway through the video show exactly how much of it to expect.