Review – Canon EF-S 24mm f/2.8 STM

 STM

Review – Canon EF-S 24mm f/2.8 STM
By: Dustin Abbott – WWW | Facebook | YouTube
Discuss the Canon EF-S 24mm f/2.8 STM

More Like This, Please!

We’ve spilled a lot of virtual ink around Canon Rumors lamenting Canon’s lack of support for their mirrorless EF-M mount, but the truth of the matter is that the EF-S mount has received an equal amount of disdain. Until the launch of this lens there was only one EF-S prime lens; the EF-S 60mm f/2.8 Macro lens (an excellent lens, by the way). There is still only one zoom lens without a variable aperture (the EF-S 17-55mm f/2.8 IS), but that lens is frankly a bit embarrassed optically by the Sigma 18-35mm f/1.8 ART lens. The release of the EF-S 24mm f/2.8 STM is thus very welcome. Who wouldn’t want an affordable, sharp prime with great maximum magnification, an awesome form factor, and a nicely affordable price? 

Want to watch your review?  Click on the video below:


I’ve owned the EF 40mm f/2.8 STM lens since its release, and while I don’t use it often, I’m in no rush to part with it because it is generally excellent and so nicely compact! Canon’s first full frame pancake lens was and is a true winner (you can read Justin’s review of it here) [by the way, I’m Dustin not Justin, but I get why you might possibly get confused around here!].  It performs great double duty on either Canon’s crop sensor (APS-C) bodies along with the mirrorless EOS M systems. The EF-S 24mm is, in essence, a repackaging of that lens specifically for crop sensor cameras (preserving that angle of view) but with a few nice little upgrades.

24mm Profile

Because I typically think in full frame focal lengths, I think of 24mm as being a fairly wide angle of view. But this isn’t a full frame lens; it is for crop sensors, so you must multiply that 24mm by the Canon APS-C crop factor of 1.6x, resulting in an effective focal length of 38.4mm, or very similar to the angle of view of the 40mm STM on a full frame camera. Don’t think of this lens as a wide angle lens but rather one that provides a nice, slightly wider “normal” field of view.

Bella

Build Quality and Handling:

When the 40mm STM “pancake” was released I praised the build quality for feeling a cut above other budget lenses like, say, the 50mm f/1.8 II. While still largely engineered plastics around a metal core, the lens felt reasonably dense and well engineered. That lens has proven durable over the past four years and has served me well. The 24 STM seems similarly well constructed and feels a bit less “plasticky” than the since updated 50mm f/1.8 STM.

Product Shots

The lens is nicely compact and scarcely takes up more room than your camera mount cap. Its diameter is nearly three times its length as the lens itself is less than an inch long (.9”/22.8mm long). By contrast it is 2.69”/68.2mm around. The weight of the EF-S 24mm is equally feathery at only 4.41oz/125g. These pancake lenses really redefine the portability of DSLRs and [almost] turn them into compact cameras. The compact nature of the lens also makes it a natural fit for the Canon EOS M3 mirrorless body via the EF adapter, and even with the adapter the EF-S 24mm seems like a native mount lens. We’ll examine its functionality in that application in this review.

Product Shots-4

The lens has an optical formula comprised of 6 elements in five groups. It has a reasonably common (and also small/affordable) 52mm filter size. The aperture iris has seven rounded blades that do a pretty fair job of keeping the aperture round as the lens is stepped down (none of that old 50mm f/1.8 hexagon nonsense!).

Product Shots-3

The lens barrel is very small, so Canon has kept things simple. There is an AF ON/OFF switch and the focus ring…that’s it (and there was barely room for that!). The focus ring is small, as expected, and like most STM lenses has relatively little resistance (or feel when manually focusing, for that matter). This is not an STM strength.

Product Shots-2

What is a strength for the EF-S 24mm is its ability to focus down very closely and provide an excellent maximum magnification figure. It can focus down to only 6.3”/160mm and has a maximum magnification of .27x, a figure that puts it among the top non-macro lenses in Canon’s staple. This handily beats the 40 STM and its .18x magnification and nearly reaches the level of the class leading Tamron 45mm f/1.8 VC’s .29x. This is an extremely useful feature and further extends the functionality of the lens as a general purpose, stay-on-the-camera option.

This close focus ability also allows the lens to shine in producing bokeh. I noted that the lens has a very nice transition to defocus though without that extreme creaminess and drawing that the higher end lenses produce. Still, if you get close to your subject you will be able to produce a nice amount of bokeh…on a budget!

Bokeh

Autofocus Observations

The 24 STM utilizes Canon’s “stepping motor” (STM) focus motor. The EF 40mm STM lens pioneered this new (at the time) approach to autofocus. While speed is always a factor with autofocus motors, STM technology is more about the way focus is achieved. Specifically, “stepping” technology is about smoothness in focus, and smooth transitions from one focus point to another. Its major application is in video capture when AF Servo focus can be used to achieve smooth video focus without hunting or pulsing. A lens with STM used with, say, the new 80D (or a number of other APS-C bodies with Video AF Servo functionality) will even do smooth, natural “focus pulls” where extreme focus changes are made from a foreground to a background subject or vice-versa. STM motors also tend to be quieter, particularly when compared to the older micro-motors used in many of Canon’s lower end (non USM) lenses.

The lens focuses quickly and accurately. I was happy with the focus speed in either viewfinder AF or via DPAF on the Canon 80D body that was my primary review camera. It seemed to me that this was one of the speedier implementations of STM that I have used.

Image Quality

IQ

If you want a more detailed breakdown of the image quality, take a look at the full review hereWith such a compact lens one might be tempted to think that optical excellence is out of the question, but I quickly discovered this was not the case.  Finally, we have a Canon branded crop sensor lens that can compete optically with the Sigma 18-35mm f/1.8 ART (the Sigma still has a bit of an optical edge, but doesn’t focus as consistently as this lens). The lens is sharp across the frame and has nice contrast. Stopping down increases contrast and resolution a bit (particularly in the extreme edges of the frame), but you can mostly use stopping down to apertures like f/5.6 or f/8 for the purpose of extending the depth of field rather than out of a need to increase sharpness. A bit of post processing helps make images really sparkle out of this lens. The only sharper EF-S mount lens from Canon that I’m aware of is the excellent EF-S 60mm f/2.8 1:1 Macro USM lens.

I was reviewing the new EF-S 18-135mm f/3.5-5.6 IS USM lens at the same time with its new Nano-USM focus system. While I LOVE the focus system of this lens, it optically cannot compete with the little EF-S 24mm prime.

IQ 2

Chromatic aberrations are well controlled with the lens. I saw a hint of green fringing in a few situations, but so low as to be essentially negligible for field use. This wide open crop from bare branches against a bright sky are a perfect storm for CA, but as you can see there is little to see here.

CA

The lens does have a bit of barrel distortion that is easily corrected (but exceeds that of the 40mm STM). The only real objectionable image quality issue is a fairly strong vignette at f/2.8 that tops 2 stops in the extreme corners. Stopping down to f/4 virtually eliminates the issue for field use, though. Here is a before/after with the standard Adobe Profile applied.

vignette

vignette-2

Flare resistance is good but not exceptional.  Wide open there is a bit of a greenish ghosting close to the light source.

Flare

By f/5.6 this has disappeared but at f/11 there is a bit of a prism effect around the light source – not enough to be an issue, however.  For most situations you won’t be adversely affected by shooting into the sun.  The seven bladed aperture produces a decent if not exceptional sunburst when stopped down to f/11.


Flare-2

The lens is capable of producing quite a bit of bokeh when close to the subject due to the close focus ability. The bokeh quality itself is not superb. The inner line of bokeh higlights is quite pronounced, meaning that there are more hard edges than what I would like in the out of focus regions and less “cream”. There is also some busyness within the circle along with some green fringing.

Bokeh Highlights

In some situations the bokeh can be a bit busy for my tastes, and it is here that the lens shows its budget nature.  The image below is a case in point.

Busy Bokeh

At the same time I recognize that bokeh is a highly subjective metric, and some of you may prefer a little more “activity” in the defocused region. I have some shots where I’m very pleased with the bokeh, so I think it may be a matter of learning the lens and shooting to its strengths.

Metal Bokeh Okay Bokeh

I am pleased with the color rendition and contrast. Neither is Zeiss level, but the box for a Zeiss lens seems to cost as much as this lens!

Nice Color

The lens also works very well as a video option. I actually purchased it specifically for a kit I was building for my responsibilities within my religious organization. We needed some video capture equipment, and I chose the EF-S 24mm to use on Canon 80D and 70D bodies for that purpose. I recently shot a whole video segment for a review/demonstration of some cycling lights with the EF-S 24mm and found it an excellent tool. You can see that video here:


The lens tracks well, has nice color rendition and even good bokeh on closer shots, and when using the 80D at 1080P/60 I was able to get very nice focus pulls by simply clicking the screen and allowing the camera/lens to do the focus pulls and then slowing them down even further in post to have really excellent results. The high sharpness at f/2.8 proved an asset, and the high magnification is exceptionally useful when wanting to shoot close, detailed shots. When used in conjunction with DPAF or similar video tracking in my EOS M3 the EF-S 24mm is a highly useful tool for a videographer. I don’t find STM focus as beneficial when manually focusing (performing linear, accurate manual focus transitions is difficult due to the ‘focus by wire’ system), but the excellent AF tracking and focus (particularly on the 80D) renders that moot part.

I mentioned the M3, and it worth mentioning that the EF-S 24mm is a fantastic option for the M series of cameras via the adapter (if you don’t happen to own the excellent EF-M 22mm f/2 STM). Many non-native mount lenses aren’t great fits on Canon’s mirrorless bodies. The need for the adapter extends the length of all lenses, making many lenses even more prone towards being front heavy and killing the balance. The EF-S 24mm joins the EF 40mm f/2.8 STM and 50mm f/1.8 STM lenses as being perhaps the most natural non-EF-M lenses to use on the system. Due to the STM focus system and light, compact nature of these lenses they perform much like native mount lenses in both size and operation. The EF-S 24mm provides an excellent “normal” angle of view on the M3, and the focus is quick and accurate via the EF adapter. The very short length of the EF-S 24mm allows the resulting lens/body combination to be small and light, fulfilling the mandate of the system (at least for me). This only extends the value of this lens, much like it has the value of the 40mm STM to me. That lens has seen more duty on my M bodies than it has on my DSLRs in recent years.

In Conclusion

There were two things that initially kept me from acquiring and/or reviewing this lens. First is the fact that I don’t shoot crop cameras all that often. When I do, it tends to be more with a small, mirrorless body that I’ve chosen for its compact size. I’ve owned the excellent EF-M 22mm f/2 STM for years and so I didn’t really need this lens. The advent of doing more and more video on crop sensor bodies like the 70D/80D is really what led me to the lens. Using it has convinced me of its value, which would be even higher if I didn’t already have a large kit of lenses and camera bodies.

City Hall

It is rare that I refer to a lens as a “must own”, but I see no reason for a person that shoots crop sensor bodies (Rebel Series, xxxD, xxD, or 7D/7DII) to not own this lens. This is perhaps even truer if you own Canon’s diminutive SL1 body. The Canon EF-S 24mm f/2.8 STM has it all. Extremely compact size, a fairly large maximum aperture of f/2.8, great sharpness at all aperture values, fast focus, and a great, highly useful maximum magnification value of .27x. The bokeh is pretty nice (if a bit busy in some situations), distortion and chromatic aberrations fairly well controlled, and even the flare resistance is quite good. There is some vignette wide open, but this can be easily compensated for either in the camera body or in post. And at $149 in the US, the highly reasonable price removes the only barrier that might cause me to hesitate to recommend the lens. It will only work on crop sensor (APS-C) cameras, but the fact that it can perform excellent double duty on one of Canon’s EOS M bodies only extends its value. The field of view of this lens is on the wider end of “normal”, which means that it is an extremely versatile focal length that functions well as a general purpose lens. This is the kind of lens that Canon needs to produce more of…but I’ll be thankful for this one for now.


Purchase Options:

Pros:

  • Extremely compact lens
  • High sharpness even wide open
  • Quick, accurate autofocus
  • Smooth video AF focus via STM
  • Good contrast and color rendition
  • Chromatic aberrations well controlled
  • Great maximum magnification value
  • Very reasonable price

Cons:

  • Fairly strong vignette at f/2.8
  • Some ghosting in the bright sun
  • Bokeh can be a little busy in some situations

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