The Canon EF 40mm f/2.8 STM is one of the oldest lenses in my camera bag. It has outlived many fancier, more expensive lenses. And I use it almost every day.
So, what is it that makes this such a great little lens? And should you make room for one in your camera bag? Read on to decide for yourself.
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Canon EF 40mm f/2.8 STM Overview and Specifications
Canon EF 40mm f/2.8 STM
This lens is one of Canon’s newer additions to the EF lineup of DSLR lenses. It was introduced in 2012. So it’s a fairly young lens as far as EF lenses go. It is among the smallest full frame DSLR optics ever made.
Today, it’s the smallest lens available for Canon DSLRs… along with the almost-equivalent crop sensor lens, the EF-S 24mm f/2.8 STM. The latter was my first lens ever. So it seemed reasonable to purchase the 40mm when I jumped ship to full frame cameras.
Besides the convenience its size provides, the 40mm is excellent optically. It outperforms its closest alternative, the 50mm f/1.8, even at f/2.8.
Another advantage it has over the nifty fifty is better close-up performance. Even by default, it’s capable of slightly better magnification. With extension tubes, however, the gap broadens.
The 40mm, with its shorter base focal length, is a more effective to-be-macro lens. And it retains sharpness much better than the 50mm at close focusing distances.
What’s in the Box?
As a fairly cheap lens, its packaging is moderate. Besides the lens (with both caps provided) and the user manual, there’s nothing else in there.
The ES-52 official lens hood is available separately. But I don’t recommend purchasing it for several reasons.
It has identical no-brand alternatives for much cheaper. It also does almost nothing to protect the lens or block sunlight with its minuscule size. Luckily, the lens’s optical performance makes it largely unnecessary.
Who is the EF 40mm f/2.8 STM For?
This lens is for everybody who basically wants to replace the body cap on their camera. Its size is ideal for quick grab-and-go shoots, photojournalism, street, documentary, and even event photography.
Even if it can’t entirely hide the fact that you’re carrying a bulky DSLR, it makes it somewhat less intrusive and frightening. This helps with portraits, especially candid shots.
It also helps to get into places where a large camera wouldn’t normally be allowed. I got away with shooting concerts on several occasions with this lens and my 5D camera.
First, that small size difference does matter. And the 40mm has the advantage there. Second, I don’t shoot portraits as often as street photography. Corner sharpness is key with the latter, so the 40mm won again. Plus, it’s a little bit sturdier built.
But I don’t recommend this lens for crop sensor cameras. The 40mm focal length is not very convenient on a crop sensor, at least in my experience. Choose the 24mm f/2.8 STM instead, which is the 40mm’s little sibling.
Mount and Compatibility
The Canon EF 40mm f/2.8 STM is primarily for full frame EF-mount cameras. These are the Canon EOS 6D, EOS 5D, and EOS 1DX/1Ds series of digital cameras and all of Canon’s 35mm film cameras since 1987.
But the lens will work perfectly on crop sensor EOS bodies (such as the 7D, 10D-90D series, and all the Rebels). It can also be adapted without loss in autofocus speed to Canon’s full frame mirrorless R bodies (currently the R, RP, R6, and R5).
I actually used it to test and review the EOS RP, as I found them to be a great, small combo.
It will work just fine on Canon’s crop sensor mirrorless EF-M-mount cameras (e.g., the M100, M50, M5, and M6). There’s just a slight drop in autofocusing speed.
You can also attach any EF mount adaptor currently used for this lens. These include adaptors to Sony E-mount, Fujifilm X-mount, Micro Four Thirds, Nikon Z-mount, Leica L-mount, and more.
Autofocusing speeds and reliability of these off-brand cameras depend on the adaptor’s quality.
The 40mm is among the best Canon lenses in this focal length range. Right from f/2.8, it provides excellent sharpness from corner to corner. It doesn’t get better beyond f/4.
As I mentioned, it retains sharpness at close focusing distances really well with extension tubes. In most aspects except with the aperture, it’s in the same league as the EF 50mm f/1.2L, which says something.
Its distortion level is excellent, barely noticeable on full frame cameras. It’s also easy to correct if you want 110% straight lines everywhere. That’s because it’s a very simple barrel-type distortion with no weird deformations.
Its out-of-focus background looks excellent. It has pleasant smoothness, no ugly transitions, and minimal longitudinal chromatic aberration. Chromatic aberration on contrasty edges is also well-controlled. It’s significantly better than the 50mm f/1.8.
Flares don’t pose much of a problem. And although they do show up, they’re quite unobtrusive and don’t result in a loss of contrast.
The Canon EF 40mm f/2.8 STM has great autofocus. But it has very limited manual focusing capabilities.
Its autofocus system is quick and very accurate. It’s responsive in very low light, too… better than you’d expect from an f/2.8 lens and better than the EF 24-70 f/2.8 II zoom lens at 40mm.
My lens has never had any issues, not even micro-adjustments required. This is in stark contrast with the 50mm f/1.8 STM. I had two faulty samples before getting a consistent one. And even that had to be micro-adjusted.
The 40mm pancake was one of the first lenses to include a stepping autofocus motor instead of the traditional USM motor, hence the “STM” mark in the name. This technology has helped a lot with smooth continuous focusing. It’s a great improvement for video shooters.
But this also means the manual focusing ring and the lens elements are no longer physically connected. This is a bummer for those who want to focus often manually.
You can’t focus when the camera is not turned on, not even in manual focus. The ring is also almost non-existent. It’s a thin plastic piece right at the front of the lens. So no manual-focus magic here.
There is no full-time manual focus override. And as expected at this size, there is no distance scale. When focusing, the front element extends out of the barrel but doesn’t rotate. Its minimum focusing distance is 0.3 m.
Handling and Build Quality
The 40mm f/2.8 STM pancake lens is mostly made of plastic, except for the lens mount, which is metal.
Despite this, it seems rather solid. And it has been taking the hits fiercely throughout years of work and travel. Marks of use, of course, are visible. But no issues of reliability have arisen.
It doesn’t have weather sealing, though. And with the moving front element, I never wanted to test just really how much this is true. This is not a rain or dust-friendly lens.
The only thing occupying the side of the lens is the manual focus and autofocus switch (MF/AF).
It has a 52mm filter thread. Filters of this size are cheap and widely available. Be aware that the autofocus motor doesn’t tolerate more than one filter in the long term. With two filters, it makes weird, whirring sounds, presumably due to the weight.
The lens is 68mm in diameter (not much wider than the lens mount itself) and 23mm long. It really is tiny. But at 130 g, it feels quite dense.
You can attach several extension tubes and still get very usable results in image quality and handling. But you’re likely limited to focusing by getting closer or farther away because of the poor manual focus implementation.
That’s not an issue with macro rails or free hand-holding. I’ve written about an excellent cheap macro setup that includes this lens.
One alternative to the 40mm pancake is the 50mm f/1.8 STM we mentioned before. It’s the newest edition of the nifty fifty.
It’s slightly cheaper and more than a stop faster. This is countered by the slightly better image and build quality of the 40mm, and the latter’s smaller size.
Also, if you’re searching for a crop sensor alternative, look no further than the EF-S 24mm f/2.8 STM.
The 40mm f/2.8 STM doesn’t take up much space. But it gives you excellent results. It’s a lens that can be your long-term partner in photography. It has definitely been mine! You can read about using this lens for low-budget macro photography.