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What is it good for?
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The Canon EF 40mm f/2.8 STM offers solid image chất lượng in a well built package that comes with the novelty of being a diminutive pancake design và at a low price point. However, slightly odd 40mm focal length might not be a great fit for your artistic vision regardless of sensor size.

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I’ve had this lens sitting in my drawer for a couple of years now, & honestly, I can’t think of when the last time was that I took it out và used it. Which to be honest, makes writing this nhận xét quite a bit more difficult than it probably needs to be.

Worse, it’s not like we’re talking about a bad lens here. Though diminutive in size, the EF 40mm f/2.8 STM packs solid image quality and a reasonably fast aperture into a tiny package with an eminently reasonable price point.

40 mm
Canon EF



4.6 oz.
0.9 x 2.7⌀ in.

One thing that can be said about Canon’s lenses for the last 8 years, or so, is that they’re being built well. There was a time, not that long ago, where I would have expected a lens like this khổng lồ feel cheap and plastic-y, & have an underwhelming plastic lens mount to lớn go with it. That’s not something that Canon seems khổng lồ be doing anymore. Even the similarly inexpensive EF 50mm f/1.8 STM isn’t built cheaply.

Build wise, the EF 40mm f/2.8 STM is quite nice, even if there’s very little lens be concerned with. The outer lens barrel is finished in a finely textured black coating that’s closer in appearance lớn an L lens than the smoother finish of many of the other consumer grade lenses.

On the rear, there’s a metal lens mount. This is a feature I always want khổng lồ see in lenses, but maybe not for the reasons some would expect. Because the lens mount interfaces with it’s counterpart on the camera body, this is a wear surface. Plastic mounts are much softer than metal ones which means that they’ll wear faster. Và ultimately, it’s the accuracy of these mating surfaces that hold lens in the correct optical alignment on the camera.



As one would expect on such a small lens, the controls are equally small. In many cases, I would consider something like a narrow focus ring, or a tiny AF/MF switch to lớn be a negative factor. However, this case is an exception. The simple reality is that there really isn’t that much lens khổng lồ start with, & making the focus ring bigger would have negatively impacted other aspects.

A perfect example of this problem can be seen in Canon’s EF-M 22mm f/2 STM for their EOS M platform. On that lens, the focus ring covers half of the overall depth of the lens. As a result, one of the complaints I had wit that lens when I was using it is that it’s hard to mount and dismount from the camera. With so much of the front of the lens being free turning focusing ring, it’s easy lớn grab the lens by the focusing ring while trying to lớn mount it and not be able to turn the in the mount.

With the EF 40mm f/2.8 STM, the focus ring is only 0.2 in. (5 mm) và only takes up 21% of the overall 0.91 in. (23 mm) depth of the lens. Quite simply, there’s much more meat to lớn grab on khổng lồ when trying to lớn mount and dismount the lens.

Additionally helping matters, Canon didn’t go for a super smooth overall design lượt thích the have with the EF-M lenses. There’s pronounced ridges along the back of the lens by the mount. These provide both a solid tactile indication that you’re holding something that isn’t going lớn spin freely on you, as well as providing good traction for turning the lens.

Of course, that still does leave a quite narrow focusing ring. However, on this lens it’s not necessarily a problem either.

Canon located the focus ring around the front edge of the lens. In fact, the focus ring here doesn’t just wrap around the perimeter of the lens, it also is the outer 6mm of the front face.

Finally, the circumference of the focusing ring is textured with a straight ridge “knurling” to provide better traction when focusing.

That said, lượt thích all STM lenses, the EF 40mm f/2.8 STM is a focus-by-wire lens, meaning that there’s no mechanical connection between the focusing ring and the part of mechanism that moves the lens elements.

The biggest consequence of electronic focusing is that the feel of turning the ring depends entirely on how the encoder & bearing system for the ring is designed. In some lenses, the focus ring feels almost identical to lớn the focus ring of a really high end manual focus lens; in other lenses, the feel fall a bit short.

The focus ring on my EF 40mm f/2.8 STM is không lấy phí spinning & smooth with no indication of grit or the rotary encoding that is being done behind the scene. Compared khổng lồ other STM và electronically focusing lenses I have, it feels a bit freer spinning than most of the others. However, that might also be a consequence of the front edge placement and that when rotating it you don’t kết thúc up rubbing as much of the barrel as you do on other lenses.

The only other control on the lens is the slightly smaller than normal AF/MF selector switch. Following Canon’s current design trends, the AF/MF switch on the EF 40mm f/2.8 STM is a flat flush mounted switch that sits in a slightly raised area in the housing. Though flat & flush with the surface, the switch is easy khổng lồ flip when you want too.

Though this is a consumer lens, & so there is less focus on manual focusing, I felt it was at least worth putting the lens through my winter glove tests. For these tests, I’ll be using two different gloves; a mix of Marmot Pre
Cip(Affiliate Link) gloves, and a set of Freehands Stretch Thinsulate(Affiliate Link) gloves.

Wearing either pair of gloves there’s no perceptible feedback that you’re touching the focus ring, at least not from the texturing. However, because of it’s position on the lens, this really isn’t necessary. You can easily feel the corner of the lens, và since that’s the focusing ring that’s all you really need.

The front filter threads are 52 mm, & don’t rotate.

In a frustrating, but typical, move from Canon, the EF 40mm f/2.8 STM doesn’t include a lens hood. Instead it’s a ridiculous $29 part that screws into the front filter threads khổng lồ mount. While I might not complain much about the $29 price if we were talking about a $1000 lens, at $130, the hood adds a further 22% to the cost of the lens if you want one.

Video Tests

Canon introduced the STM motor in conjunction with their greater focus on đoạn phim DLSRs. The motor replaced the traditional, and loud, micro motors, and silent, but less than smooth, micro-USM motors with something that could silently make smooth focus transitions.

With the focus on video clip for the motor system, it’s worth at least looking at the rest of the lens in that context.

The first question goes lớn manual focus. Controlled smooth focus pull is an important aspect of cinematography. & that’s also a place where this lens falls down a bit.

To start with, the manual focus ring is pretty small, though the texturing is gear-tooth like and may mesh with some follow focuses. However, the diminutive form size is going to make it hard to lớn mount a follow focus in the first place.

Secondly, because the lens is purely electronic, there are no stops for infinity and close focus. In fact, in my testing, the electronic focusing system seems lớn take things a step further & vary the relationship between ring rotation & focusing shift based on the speed at which the ring is turned. That is, turn the ring slowly, and the lens focuses in smaller increments making it more sensitive. Turn the ring quickly, & the lens jumps faster but with less sensitivity.

The result of this is that while the lens can easily be manually focused, & focused accurately, its not repeatable. It also means that focus pulls can be somewhat erratic.

With that out of the way, lets move on khổng lồ breathing. Breathing is caused by the lens’s angle of view shifting while focusing.

This lens breathes.

I don’t even have to test for it, as this is an overall linear extension focusing design. That means that the khổng lồ focus closer to lớn the camera, all of the lens elements move away khung from the sensor. This has the effect of changing the effective focal length và therefore the angle of view.

What is it good for?

Well, the answer certainly isn’t, “absolutely nothing.”

40 milimet is a bit of an odd ball focal length, at least in the traditional context of lenses. It’s about 14% longer than the traditional 35 mm, and about 20% wider then the next step up at 50 mm.

That said, I believe it was Ernst Leitz, the man who founded Lecia Camera, that argued that the proper “normal” focal length was for the focal length khổng lồ equal khổng lồ the diagonal of the film frame, và only later settled on 50 mm. For a 24 x 35 milimet frame, that would be 43.26 mm, & 40 mm is a lot closer to that than 50 mm.

In many ways, this lens is right in a sweet spot, all be it a non-traditional one, for normal lớn slightly-wider-than-normal lenses.

All that said, as I noted at the start, my copy has largely lived in my lens drawer, & that’s something of a contradiction given that I keep saying the lens isn’t a bad performer. This is where lens choices become something of a personal decision.

To start with, the 40 milimet focal length doesn’t really vị much for me artistically. Normal và slightly wide lenses just don’t địa chỉ cửa hàng much in the way of interest lớn images. & while the resulting images may be more reflective of reality, or how my eye supposedly saw the world at the time, they image they produce certainly isn’t reflective of how my brain perceives the world.

Compounding matters, I also own Canon’s very good EF 24-70mm f/2.8L II USM zoom. Optically, the two are very close. Though with the prime being a prime it does beat the zoom in terms of resolution. However, with both lenses being f/2.8, the choice, for me, ends up being between a zoom that has focal lengths I lượt thích to shoot at, and a prime that doesn’t. Under those conditions, the choice really isn’t that hard for me to lớn make.

Does this mean that you should avoid the EF 40mm f/2.8 STM? Absolutely not.

Smaller than a 1.4x teleconverter, the diminutive form size of the EF 40mm f/2.8 STM makes does have a novelty factor.

The lens has a lot of things going for it. It’s small kích cỡ makes is a unimposing lens for things like street photography or really anywhere you might want to lớn have a lower profile camera. At f/2.8 it’s reasonably fast, though it is still a stop-and-a-half slower than the slightly cheaper EF 50mm f/1.8 STM. And rounding out the package, it’s relatively inexpensive at around $130.

It was the solid optical performance, small size, và low price that got me to buy one of these lenses, và it’s the small form size and solid performance that has me keeping it around, even after I’ve sold other lenses.

That just leaves the question, where does the EF 40mm f/2.8 STM fit, & is it a good lens to lớn have in your bag?

This is a question that’s somewhat hard for me khổng lồ answer. In some respects the lens is very much just a novelty due to lớn the pancake design. The EF 50mm f/1.8 STM is faster và slightly cheaper, & honestly not all that much bigger.

I would say that the EF 40mm f/2.8 STM is a reasonably poor-man’s 35mm prime, và in many ways it is. But at the same time, Canon does make a 35mm f/2 IS USM that is both actually 35mm, a stop faster, & image stabilized.

Aside from the novelty factor, I’m rather hard pressed lớn come up with a compelling reason to have one of these.

One place where it might really shine is on an EF-EOS-M mount adapter and attached to an EOS-M. The pancake design, even with the mount adapter, keeps it reasonably small on the small mirrorless bodies. Moreover, on an APS-C camera the lens gives an 64mm equivalent angle of view, making it more of a short portrait lens. Though it’s still a bit of an odd focal length.

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The diminutive Canon EF 40mm f/2.8 STM Pancake Lens immediately inspires the high-pitched talking-to-a-baby voice from its first-time viewers, with short drawn-out words và phrases such as "awwwwe" và "it"s sooooo cuuute" being especially common.It is of course the form size and weight of this lens that triggers this response.


The EF 40 STM enters the world tied with the Canon EF 50mm f/1.8 II Lens for the lightest Canon EOS lens designation.And, being just over half as long as the 50 f/1.8 II, easily shatters the length record.This lens is even shorter than a Canon 1.4x extender (comparison below).


But the kích cỡ of this lens is not the only reason lớn not take it seriously.The pancake"s breakfast-level price ranks it near the bottom of all currently available Canon lenses.You could buy 70 of these for the price of one Canon EF 800mm f/5.6L IS USM Lens.How many 40s would it take lớn consume the volume of one 800 L is a question I"m still pondering.

It is indeed hard to take such a tiny, inexpensive lens seriously, but don"t write the EF 40 STM off too quickly.


With new acronyms in the model name, let"s start this review with some quick definitions.You know what "Canon" means. You know what "Lens" means.40mm is of course the focal length of the lens."EF" means that this lens will mount và function properly on all Canon EOS cameras produced to date.The new acronyms are "Pancake" and "STM"."Pancake", in lens speak, refers to lớn a short, flat shape."STM" stands for "Stepping Motor" - a motor that moves or rotates in small discrete steps (more info later in the review).


With that understanding, let"s move khổng lồ an important lens decision factor - focal length.When choosing a lens, focal length should be one of your top selection priorities.

Falling between the wildly-popular 35mm & 50mm focal lengths, Canon"s 40mm focal length choice is an interesting one.While a 40mm lens sounds close to a 50mm lens (and the two can often be used interchangeably),there is a difference in the perspective these lenses provide when identical framing is used.

In the example below, the sides of the frame are nearly identical for each example focal length,but the large trees in the background change kích thước greatly in proportion to the foreground due lớn the different focus distances required for the same framing.


These examples were shot with a full frame camera.The same lenses used on an APS-C camera would of course frame more narrowly (40mm frames like 64mm on APS-C),but perspective differences would still show in identically framed shots.

The wider angle lens will emphasize what is closer khổng lồ the camera in relation lớn the background.The wider angle lens will also emphasize human subjects" closest parts - often noses - making them noticeably larger in relation to lớn the rest of bodies if used at a close distance.40mm is not a good head shot portrait lens.

Step back and your subjects will be happier with their portraits.Portraits (not framed tightly) are but one of a huge range of uses for a 40mm lens.40mm is a focal length that you could leave mounted for general purpose needs.

A downside lớn using a single focal length for all of your images is that your images can all begin to lớn look similar.My preference is khổng lồ use a range of prime lenses - in no more than một nửa or 2x focal length increments.

Adding lớn its multipurpose capabilities is the relatively wide f/2.8 aperture.While not wide for a prime lens in this focal length, f/2.8 is as wide as zoom lenses get.An f/2.8 aperture is usually what I consider minimum for stopping motion indoors.Here is an outdoor motion-stopped example.


The sample picture above was captured with the Canon EOS 5D Mark III.Settings were ISO 200, f/2.8, 1/1250, AI Servo AF, Burst Mode, 5300K white balance và the Standard Picture Style.A B+W 52mm XS-Pro Kaeseman Nano Circular Polarizer was utilized for this shot.

Not surprising with its small size is that the 40 STM Lens forgoes image stabilization.The relatively wide f/2.8 aperture makes this feature less missed.This lens is handholdable in lower light conditions.


Small kích thước and small price are great, but ... Image quality is a sacrifice one would expect to make khổng lồ gain these attributes.Amazingly, this lens delivers impressively in this regard.

The Canon EF 40mm f/2.8 STM Lens is very usably sharp at f/2.8 with a modest increase in softness as the outer portion of the image circle is reached.Stopping down to f/4 results in a sharp image across the frame save the extreme full frame corners.At f/5.6, even the extreme full frame corners are very sharp - allowing this lens khổng lồ compete with lenses at far higher prices.

The ISO 12233 chart comparison tool will show you firsthand what these results look lượt thích - & will allow comparisons with the rest of Canon"s lenses.Find this links at the đứng đầu of the review.

At f/2.8, the EF 40 STM shows about 2 stops of vignetting in full frame corners.This is a noticeable amount, but not a severe or surprising amount.Half of the vignetting is gone at f/4, but .6 or .7 stops remain throughout the balance of the aperture range.As usual, APS-C users will not have to worry about vignetting from this full frame-compatible lens.

CA (Chromatic Aberration) is very well controlled - nearly absent.Same with flare.Even with the sun in the full frame corner, flare is hard khổng lồ notice.Flare performance is certainly advantaged by the use of only 6 lenses in 4 groups.

The 40 STM has very minimal distortion.

Utilizing a circular 7 blade aperture, the 40 STM delivers a nice background blur chất lượng as shown below.


A 40mm f/2.8 lens is not going khổng lồ set any background blur records, but when used at f/2.8 và a short focus distance, the background goes nicely out of focus.


The site"s ISO 12233 chart tool is ideal for directly comparing lenses to each other, but I took a couple of inexpensive & relatively similar lenses outdoors on a clear day for another comparison with the 40 STM.You will likely recognize these images as being the bottom right crop from the perspective comparison shown near the beginning of the review.

Compared at the link below (click on the image) are the Canon EF 35mm f/2.0 Lens, Canon EF 40mm f/2.8 STM Lens and
Canon EF 50mm f/1.8 II Lens.


Extreme full frame corner crops will show a lens at its worst.

The Canon EF 50mm f/1.8 II Lens is very well regarded for the image quality (sharpness) it delivers for its extreme low price.While it is a bargain, it is extremely low kết thúc in all other regards including build unique - which includes a plastic mount.My first 50mm f/1.8 II fell apart.It physically broke in half for no apparent reason.

The 50 f/1.8 II compared here was purchased specifically for this review.The replacement lens does not perform as well as my first one did - I vì chưng think it is an inferior copy.But, it sure makes the 40 STM look amazing.The build quality difference is also as night và day.

The Canon EF 35mm f/2.0 Lens is another inexpensive lens with an even closer-to-40mm focal length.This lens is sharp in the center of the frame, but does not have a flat plane of sharp focus - và corners are especially not rendered well.

The 50 f/1.8 II và 35 f/2 both have the wider aperture advantage.The difference between f/2 và f/2.8 is one stop - one stop is a 2x difference in the amount of light delivered to lớn the sensor.If you don"t need that extra stop, the 40 STM is, in my opinion, the best option of this group.


The 40 f/2.8 STM Lens is the first available Canon lens with the stepping motor AF implementation.The Canon EF-S 18-135mm f/3.5-5.6 IS STM Lens was simultaneously announced,but showed up in stock only as I put the finishing touches on this review.

While I definitely prefer Ring USM focusing systems better, the STM kiến thiết works well.It focuses reasonably fast and most importantly, accurately.

The STM design is a focus-by-wire AF implementation.FTM (Full Time Manual) focusing is supported (if enabled for electronic manual focusing lens is selected in the camera"s thực đơn - the default),the focusing ring does not turn during AF.The lens" switch must be in the "MF" position - and the camera meter must be on/awake - for manual focusing.If the meter is inactive, MF does not function.

The focusing ring size, like that of the rest of the lens, is tiny.However, being positioned at the outer-most position on the lens barrel, the MF ring is still quite usable.It easy khổng lồ rotate và reasonably smooth.Expect some modest subject form size change in the frame when pulling focus on this lens.The front filter threads do not rotate with focusing, though the lens" inner barrel extends modestly at minimum focus distance.

There are no focus distance or DOF markings provided.There is no room for a window for such, & since the focusing ring is not directly connected to the focusing gears (same as with USM AF implementations), printed markings are not available.Most AF lenses produced today have no significant DOF markings.I doubt that anyone using this lens will care about these missing features.


The Canon EF 40mm f/2.8 STM Lens was introduced with the Canon EOS Rebel T4i / 650D DSLR.The T4i press release revealed that "When used with Canon’s new EF & EF-S STM lenses, the camera can provide smooth and quiet continuous AF while recording video."I don"t doubt the "smooth" portion of that claim, but I"m more skeptical of the claim that the Rebel T4i will not capture focus motor sounds during đoạn clip recording.

My T4i Kit did not ship as of reviews time, but I can tell you that the 40 STM is not a silent focusing lens.While not as noisy as the Canon EF 50mm f/1.8 II Lens for example, the 40 STM emits a buzz when focusing. The noise is not bad, but I vì expect some buzzing motor noise lớn be picked up by an in-camera microphone even on the Rebel T4i/650D -unless a sound cancellation or other công nghệ is employed.

Update: Confirmed. The 40 STM"s AF sound is easily audible in Rebel T4i đoạn phim when using the built-in stereo mic.

In AI Servo mode, the 40 STM performs quite well.Honestly, I thought it would fall apart when given a reasonably challenging target.Of course, finding challengingly fast moving subjects that fill a 40mm frame (and bởi not impose a safety hazard khổng lồ the photographer) is a bit of a challenge.The DOF at 40mm và f/2.8 is rather deep at the distances most often used for this purpose.My hit rate on the cantering/jumping horse shown above was quite high.

I much prefer the 40 STM"s focusing system lớn the systems found in the Canon EF 35mm f/2.0 Lens and Canon EF 50mm f/1.8 II Lens.

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The 40 STM"s 11.8" (300mm) MFD (Minimum Focus Distance) will deliver a 0.18x mm (Maximum Magnification).This is a relatively low value, but a typical value for a prime lens.Here is how other Canon options compare:

Canon EF 24mm f/1.4L II USM Lens9.8"(250mm)0.17x
Canon EF 24mm f/2.8 IS USM Lens7.9"(200mm)0.23x
Canon EF 24mm f/2.8 Lens9.8"(250mm)0.16x
Canon TS-E 24mm f/3.5L II Tilt-Shift Lens8.3"(210mm)0.34x
Canon EF 28mm f/1.8 USM Lens9.8"(250mm)0.18x
Canon EF 28mm f/2.8 IS USM Lens9.1"(230mm)0.23x
Canon EF 28mm f/2.8 Lens11.8"(300mm)0.13x
Canon EF 35mm f/1.4L USM Lens11.8"(300mm)0.18x
Canon EF 35mm f/2.0 Lens9.8"(250mm)0.24x
Canon EF 40mm f/2.8 STM Pancake Lens11.8"(300mm)0.18x
Canon TS-E 45mm f/2.8 Tilt-Shift Lens15.7"(400mm)0.16x
Canon EF 50mm f/1.2L USM Lens17.7"(450mm)0.15x
Canon EF 50mm f/1.4 USM Lens17.7"(450mm)0.15x
Canon EF 50mm f/1.8 II Lens17.7"(450mm)0.15x
Canon EF 50mm f/2.5 Macro Lens9.1"(230mm)0.50x
Canon EF-S 60mm f/2.8 Macro USM Lens7.9"(200mm)1.00x
Canon EF 85mm f/1.2L II USM Lens37.4"(950mm)0.11x
Canon EF 85mm f/1.8 USM Lens33.5"(850mm)0.13x

Wide angle & normal focal length lens MFD/MM values typically change dramatically when used with extension tubes.The
Canon EF 12mm Extension Tube II takes the mm value 0.50x and the Canon EF 25mm Extension Tube II takes the milimet value 0.88x.This lens is not compatible with Canon"s extenders.If you look at the comparison photo at the đứng top of this page, you will see that it appears lượt thích the extender would protrude half way through the 40 STM.