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This lightweight little lens is surprisingly good for the price. 40mm has become a popular focal length over the past couple of years. Manufacturers have realized that it’s easier to make than a lot of other focal lengths; photographers appreciate the slighter wider look from the standard nifty-fifty; and filmmakers are aware that it’s actually one of the more common lengths in Hollywood. It’s very close to the angle of view of the human eye, though our eyes are never so still that we’d notice. There have been a number of films shot almost entirely with a single 40mm lens, The Godfather being one of them.

The Viltrox AF 40mm is truly a budget lens, currently priced at about $170. The lens is plastic, and very light in the hand, which is to be expected at this price point; but it also feels fairly well constructed. It’s not meant for rugged wear-and-tear like my old Nikon lenses, but it’s not going to fall apart on its own. The small sun hood borders on silly, and there’s no weather sealing whatsoever. It weighs just 170 grams, and has a USB-C port in case there are upgrades (which I doubt).

I tested the Viltrox AF 40mm with a Sony a1, a 50MP camera that’s very unforgiving to cheap lenses. Honestly, I was expecting to see a lot of shortcomings, but the Viltrox is quite sharp wide open in the center, with an acceptable amount of softness on the edges. I wouldn’t place my subject farther than the rule of thirds with this lens at 2.5. By f/5.6 it’s razor sharp all the way across the frame. On a 40mm, F/2.5 is fairly shallow. It’s not great for specialty, super shallow images that are all the rage in YouTube short content, but for more ambitious content, it does just fine.

The Viltrox has good contrast and color, too. It reminds me of the Samyang 45mm, which is renown for its punchy colors and balanced contrast.  This little lens does a fairly good job of resisting flare, too (for its price point). As expected, there’s some wash-out when pointed towards the sun, but nothing extreme.

If we take a quick look at the MTF chart, we see fairly impressive contrast and resolution at the center (78% resolution wide open and 82% at f/8. The separation of the solid and dotted lines roughly midway across the center gives some numerical context to the slightly chaotic Bokeh in the transitional zones. (If you’re unfamiliar with MTF charts, the thick lines represent how the lens performs with a lower resolution sensor, and the thinner lines show how it performs with a higher resolution sensor; higher lines on the chart is better, with anything above 0.7 being very good performance. The X axis– reading 0-20– the distance from the center of the sensor [0] to the farthest corner [20]).

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Its autofocus is decently fast in both photo and video modes, but more importantly its confident. It takes and holds focus well. f/2.5 isn’t the brightest aperture for a lens– there are plenty of 1.8s out there– but its quick and bright enough for most uses. Focus ring which turns extremely smoothly…. I’d prefer a little more resistance, but too little is better than too much. It works with face and eye detection on Sony cameras. It uses a wire mechanism, which is typically a disadvantage because the speed in which you turn the ring changes how it ramps the focus in a non-linear, un-repeatable way. A quarter twist the ring quickly and a wire mechanism will speed through the focus range; twist it slowly and the same stopping point results in a different focus distance. But the Viltrox is linear, so the same spot on the ring will be the same focus depth. The Viltrox suffers from only a small amount of focus breathing.

It’s a budget lens, so there are shortcomings. The weakest point of the Viltrox is its bokeh, which is a little bland; it does transition from sharp to blurred smoothly, but its a little clinical. The aperture tops out at f/16, which is fine for most photography but a little painful for videographers. There’s a noticeable softness from diffraction at f/16, so you’ll probably want to stay at f/11 or below.  Remembering your Sunny 16 Rule (f/16, 100 ISO, 100 Shutter speed is perfect exposure on a sunny day), you’ll see that you’re going to need a good ND filter even if you aren’t interested in shallow depth of field.

CA certain amount of vignetting is expected with most any lens, and budget lenses tend to perform badly. The Viltrox does well for a budget lens, but can’t compete with higher priced 50mm. There aren’t many 40mm lenses to compare it with.

Lens distortion, on the other hand, is a completely different matter. Here the Viltrox performs exceptionally well. There’s virtually no distortion whatsoever.

Considering the price point (which is roughly half that of many others) the bokeh and slightly slower aperture are small trade-offs. From a cinematographer’s standpoint, the solid performance of the autofocus is much more important. It’s a good choice for interviews and as a general walk-around lens if you don’t have a solid zoom on hand. Its feather weight may help with your gimbal work or just take the stress off your back. If you’re on a budget, or just want a 40mm to add to your collection, this Viltrox 40mm lens is a very good choice.