What is It?
The 40mm f/2 is what I'd call a "muffin size" lens. Not so small as to be a pancake-type lens, but also not large enough to be something you need to pay attention to. It's more of a snack of a lens than a full meal. It's a compact lens at only 2.8" (70mm) long, and a light one, too (at 6 ounces, or 170g).
Nikon Z System users have been asking for compact primes pretty much since the introduction of the Z6 and Z7, and the 40mm f/2 is Nikon's second (and not last) response (the 28mm f/2.8 came first).
Optically, it's reasonably simple and old school with only a token of modernization: 6 elements in 4 groups (old school), with two of the elements being aspherical (a modernization). Most of the glass mass is at the back of the lens. The aperture diaphragm stops down to f/16 and is electronically controlled, as with all Z-mount lenses. The diaphragm features 7 rounded blades, an improvement over the other muffin, the 28mm. No special optical coatings are used, though Nikon's ubiquitous Super Integrated Coating is present. Up front we once again have 52mm filter rings to match the 28mm.
The focus is done via a single stepping motor. Focus is internal, and has a minimum distance of about a foot (.29m). That puts the maximum magnification ratio at a very meh 1:5.9. While Nikon suggests that the lens doesn't focus breath for video, I could detect a small amount of change if you rack completely from minimum focus to infinity. For most focus moves, no, you wouldn't see any focus breathing.
Also meh is that there really isn't anything else to distinguish the lens: no switches/buttons, no extra ring, nada.
Nikon not only doesn't supply a lens hood with the 40mm f/2, but they haven't specified one, either. Amazon has a reasonable screw-in choices: the Digital NC and F-Foto HF-52 [affiliate links: As an Amazon Associate I earn from qualifying purchases]. Both are a little wider than need be, but both keep a fair amount of stray light from the front element.
The lens has some dust and drip sealing, but the design doesn't really have any ingress points for water. The lens mount is polycarbonate, not metal. I don't judge that to be an issue; Nikon uses a very hard polycarbonate that actually withstands wear better than some of their metals.
The 40mm f/2 is made in Thailand and only styled like modern Z-mount Nikkors (unlike the 28mm f/2.8, which had a legacy style SE version).
Price is US$299.
Source of the reviewed lens: purchased.
How's it Handle?
As with most of the Z System primes, there's not much to talk about. The fly-by-wire focus ring is easy to find and smooth.
How's it Perform?
Focus: Given its price and size, I wasn't expecting anything special in the focus category, and that's what I got: nothing special. The 40mm f/2 is faster to focus than most of the F-mount f/1.8 lenses, but that's not saying a lot. In most circumstances, I don't see the change in focus or hear it during autofocus, which means to me it's fast enough. Video users will find that there's minimal focus breathing.
Sharpness: I find this lens a little more difficult to describe than usual, as I see some slight differences that are possibly caused by having two of the only six elements have aspherical properties.
The center is very good at f/2, and clearly improves to excellent by f/2.8. I see small improvements above that out to about f/5.6, where it is clearly excellent. The far corners are only a "soft" fair at f/2 (low contrast), improve to good by f/4, and continue to improve through f/5.6, where I'd rate them as good+/very good-.
In the intermediary areas between center of frame and corner I see differences that are difficult to explain. At first pass, I'm going to say that this difference is distance influenced. For example, at f/2 the mid-frame (measured at the DX corners) seems to be good, but there is strong variability between near and far focus. Things improve to very good at f/2.8, with less distance impact, and that trend seems to be consistent through to f/8. If I were to guess, I'd say that there was a tendency to make far performance optimize first over near performance. Indeed, at the minimum focus distance, even the center has reduced contrast and MTF compared to a more normal testing distance, and the corners aren't usable until about f/4.
On a test chart at moderately close distance the lens performs best at f/4 in the center, but the mid-range frame does something interesting and drops some at f/4 before rising to best performance at f/5.6. Corners don't hit best performance until f/8 at close focus distance.
Short answer: the lens is very usable in much of the frame wide open, but if you're trying to exhaust every bit of its resolving capability corner to corner, you'll really want to be at f/5.6, maybe f/8. The old rule of thumb of stop down two stops to reach maximum performance does not seem to evenly apply to this lens, though. I've seen other reports that say performance is maximized at f/4, but that's not what I measure and see, and particularly the further I move focus outward. One other review said the 40mm appeared to be about equivalent of an old Double Gaussian design from 15 years ago. I wouldn't quite go that far, but the lens is decidedly old school in one respect: stop down to get best results.
This lens has clearly visible coma. It's not an astrophotography lens by any stretch of the imagination. Spherical aberration is actually better than I'd expect given the other traits, though.
Note that the lens also has clear focus shift, so if you're using apertures slower than f/5.6 you might want to pay attention to that, and you probably want to refocus any time you change aperture. "Covered by depth of field" is not the same as "accurate focus plane," and the closer you are to the subject, the more you can be penalized by that with this lens.
Chromatic Aberration: Substantive longitudinal CA wide open, which takes a couple of stops to mitigate. Lateral CA is well controlled, particularly by in-camera corrections.
Look carefully at the sky (image out of camera with no lens corrections).. When CA is significant, you often see a color impact on high contrast areas such as the intersection of tree detail in shadow and sky. There's a bit of a magenta shift here, and given its location and appearance in the image, I'd say the longitudinal CA is the culprit.
Linear Distortion: Very minimal barrel distortion without in-camera corrections. Minimal enough that many won't correct it (e.g. less than 1%). Corrections are pretty much linear.
Vignetting: Strong vignetting in the corners wide open, above 2EV. The image circle is quite evident at f/2, where even the DX corners would show some vignetting. As with a lot of Nikkors historically, for some reason the image circle on my sample is slightly lower than center (though sensor VR can also cause the circle to move). In camera correction doesn't really "flatten" the corners until f/5.6, but that's also the aperture at which uncorrected results start to show an image circle than somewhat includes all corners.
Flare: With light sources well into the frame, the 40mm f/2 tends to produce at least one obvious colored flare spot, typically green or blue, and this can echo in some situations. Light sources in the extreme corner or just off the image area don't tend to produce similar flare. I found this characteristic to be curious, to say the least, as it's almost the opposite of what we usually find with lenses. The lens does produce impressive sun stars when stopped down (18 rays that become obvious at f/11).
Bokeh: Bright edge ring and some clear onion-skinning, and mostly devoid of Longitudinal CA color fringing once you're at f/4. Some visible clipping in the corners, but I can't really call it cats eye, as it appears to be only one side that's getting clipped. On DX cameras, clipping is mostly ignorable at f/2.8, but you really want to get to f/4 to restore a fully round blur.
Final Words
At US$300, the expectations for this lens are both exceeded and not met. Optically, the lens probably exceeds expectations. It's a very good optic, and almost a bargain in that respect at the list price. On the other hand, I suspect many will find the lens "not small enough." You can't call the 40mm f/2.8 a pancake lens. It's really what I call a muffin lens (about the size of a modest breakfast muffin).
The combination of optically fine and not-quite-small-enough probably provokes some buying angst for some, when it really shouldn't. Say what you will about the size, but this is such a light lens that it's really not a burden to carry, and I'm not finding the size to be a real issue.
I think the bigger issue for many is whether or not 40mm (or f/2) value is the right choice. The classic "street lens" angle of view would be better served at 35mm, not 40mm, for instance. While the more common "normal" lens angle of view would be better served at 50mm (and loose portraits at closer to 60mm). At f/2 with high vignetting, it might not be as fast a lens as people want, either. Thus, the specs are a bit of a tweener, not exactly satisfying any crowd.
I'm fine with that. Moreover, on a Z50 or Zfc, the 40mm f/2 lens is a "short portrait" focal length (60mm effective), which gives me an option for DX that I like, and the optical properties all tend to be fine at the DX crop. Think of it more as a torso up portrait lens than a head and shoulders one on DX.
For those of you who are metalists, get over it. The poly carbonate used in both the exterior and lens mount of this lens is fine. Indeed, I've tended to find that most metal-mount lenses brass over time, which means that small metal shavings head towards your image sensor over time. I haven't found the poly carbonate that Nikon uses in lens mounts to do anything similar. I do wish Nikon had added a rubber weather seal at the mount, though.
Plenty of folk are going to embrace this muffin of a lens. Nikon has priced it well for what it is and does, and the compact nature adds an important capability to the Z-mount offerings that some will want. It's not quite a "bargain" lens, but it's close (it's often on sale with enough of a discount to call it a bargain). I'm probably more of a 28mm f/2.8 muffin guy than a 40mm muffin guy, but I'm sure Nikon will find plenty of takers for the 40mm f/2. My advice to Nikon: keep the muffins coming. A 20mm f/3.5 and a 60mm f/2.8 would be highly welcome given what we've been given so far. Of course, we also have the "large muffin" 50mm f/2.8 MC to consider, as well.
Recommended (2022)
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