Review: Canon EF 50mm f/1.8 STM



Review –  Canon EF 50mm f/1.8 STM
By: Dustin Abbott – WWW | Facebook | YouTube
Discuss the Canon EF 50mm f/1.8 STM

We here at Canon Rumors are all too familiar with the “Canon Two-Step”. As other companies innovate we all pull our hair out wondering what is wrong with Canon. Canon has made a habit in recent of years of not building the lenses that we all guess they are going to build while often announcing and then swiftly releasing lenses that few people expected.  After Canon refreshed a number of its smaller, non-L series primes (24mm, 28mm, and 35mm) with critically acclaimed (and image stabilized) new designs, the common expectation was that Canon would next address its aging yet popular EF 50mm f/1.4 USM.  So what did Canon do?  The opposite of expectations, of course, and instead released a refreshed version of its “plastic fantastic” aka “nifty-fifty” aka EF 50mm f/1.8 II.  That new lens is the EF 50mm f/1.8 STM, and while it may not be the lens that many of us were desperate for, it is a solid new lens and a smart move by Canon – this is probably the best cheap 50 in the world now, and will move a TON of copies. But is it a lens for you? Let’s jump in and find out!

We knew from the press releases that Canon had made a number of significant changes to the design of the age old 50mm f/1.8 formula while leaving a few things untouched. Here is a quick list of the changes:

    • Redesign of the aperture iris.
    • Shorter minimum focus and maximum magnification.
    • Better build quality, including a metal mount.
    • Replace micro-motor with new STM focus system
    • Better focus ring.
    • Better coatings. From Canon's press release, “Composed of six elements in five groups, the new Canon EF 50mm f/1.8mm STM lens features an optimized lens placement and Super Spectra Coating (SSC), translating into less ghosting and flaring than the previous model, while at the same time helping to enhance light transmission and optimize color reproduction accuracy.”
    • Even more compact size. The “nifty-fifty” was never a very big lens, and while the new lens isn't the pancake lens that some had hoped for, it is a truly compact lens. The previous lens was about 41mm long while the new lens is about 38mm. The new lens weighs about 30grams more, but that is still only 159 grams, and that is a great news as it reflects the more robust build quality of the new lens. By comparison, the EF 40mm f/2.8 pancake weighs 130g and is 23mm long.
    • Exact same price.

How does the actual lens hold up to the price release bullet points? Well, after spending the past month with the new lens, here is what I’ve found.

Build Quality
The new 50STM is a very nice lens for its extremely low price point. It feels like a real lens rather than the toy-like quality of the “plastic fantastic”. I let my wife and children handle the old 50mm f/1.8 II, and they were shocked at cheap and “plasticky” it felt in comparison to the usual volume of lenses flowing across my desk. The 50mm STM is small and light, of course, but it feels like a real lens.

The new 50 STM has a slightly more matte finish that what I’ve seen on a Canon lens before. The focus ring is still on the smallish side, but is wider than the focus ring on either the older 50mm f/1.8 or that on the 40mm STM.

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One negative carried over here from the previous generation is that the lens is NOT internally focusing. The internal lens housing does extend during focus. It is most pronounced at minimum focus and is fully retracted at infinity focus. Most annoying is the fact the lens housing does not retract when the camera is powered down, and the nature of STM technology means that you cannot manually retract it when the camera is powered off. That exposes a vulnerability, as it might be possible to damage the lens by something hitting that front barrel when it is extended. It makes the purchase of a lens hood an important consideration. The lens hood would prevent that happening in most all situations.  Yes, nearly $27 for a piece of plastic is a bit ridiculous, but considering the bargain price of the lens, just consider it part of the investment.

Some photographers were hoping that this lens would be a “pancake” like the 40mm f/2.8 STM. While it isn’t really a pancake, for all practical purposes it is almost as good. It should easily slip into a jacket pocket and be very easy to bring along, and will add next to no discernable weight to most photographer’s bag. I should also note that the compact size of the lens and its use of STM makes it a very natural lens to use with the EOS M line of camera bodies via the EF adapter.

The reality is that Canon has given us far more lens and charged us no more for it, making this lens officially one of the best bargains (if not the best) in DSLR photography. Canon’s margin on this lens is probably initially going to be fairly small (despite recycling a fair portion of the optical formula), but I have a feeling that they will make up for it in volume. This lens is cheap enough that many photographers will buy it even if they don’t intend to use it that often. I’ll probably do it myself, and that’s why Canon was very smart to keep this lens priced so aggressively. It also deflects the attack from Chinese maker Yongnuo with their “clone” of the 50mm f/1.8.

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The key component of this upgrade is found in the name: STM. STM standings for “Stepping Motor”, and it is a newer focus motor technology that began with the EF 40mm STM lens.  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. 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.  Take a look at the difference in the focus quality and sound during AF Servo video capture on a Canon EOS 70D body.

The older 50mm f/1.8 II lens was one of the most notorious examples of the downsides of micro-motor focus. Its AF was loud, buzzy, and had a scratchy sound like it was working through a bit of grit every time. Micro-motors do not support full time manual override, so you would have to select manual focus on the side of the lens before attempting to manually focus with the tiny manual focus ring that seemed to be barely attached to the very front of the barrel. Not great. It felt much like its price – cheap.

The STM version is a big step up. The focus motor is noticeably quieter (though not silent nor as quiet as other STM lenses that I’ve used), and it is much smoother. Faster? Not noticeably, but definitely smoother. Check out this video for a look at the build, motor, and focus sound.

I should note that the copy of the lens that I reviewed did require significant AFMA adjustment (focus tuning) on the bodies that I used it on (save the EOS M, obviously). This included two Canon 6D bodies and 1 Canon 70D body. On all bodies the AFMA was at least -11. That is one of the more extreme adjustments that I have had to make on a modern lens, but on a positive note the result was consistent across multiple bodies and was repeatable in multiple tests. If you have a body that does not support AFMA adjustment and find that your copy of the lens is not focusing consistently (accurately), you might consider sending the combination (body + lens) to Canon for calibration. It might cost you a bit of money but will save you a lot of heartache.

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This lens has not changed my mind about manual focus or MF override in an STM lens. The camera has to be awake and prepared to accept input from the lens before it will do anything at all, and even then, there is a lag when making manual adjustments because the manual input is sent to the focus motor that actually makes the adjustment. This is sometimes called “focus by wire”, so true manual focus is nonexistent.  I still prefer a quality USM (or equivalent) focus motor.

Image Quality
Canon has not made a lot of claims of improved optical performance from the lens, even coming out and saying that it uses the same optical formula as the previous lens. It seems like they are being modest, however, as I do perceive a very slight bump in resolution (particularly towards the center) along with noticeably better contrast.  What Canon does claim is that the optical formula has “optimized lens placement”, and that has produced a better image overall. It is very modest jump, but when one considers that we are getting a vastly improved lens in other ways for the same money, it still feels pretty good.  Better contrast helps to create the impression of slightly better resolution. In some situations the image quality looks identical, while in others I do see a bit of an improvement from the new lens.  Here are some crops that show direct comparisons.  I notice a considerable difference in the center on a crop sensor in this comparison:


I see less difference in the center on this full frame comparison, but there is a slight improvement across the frame, mostly in the perception of less “haze” due to reduced contrast and resolution. If you are interested in more detailed analysis of the image quality and comparisons to the EF 50mm f/1.8 II, the 40mm f/2.8 STM, and a vintage SMC Takumar 50mm f/1.4, check out the full review here:

The good news is that the image quality was already pretty good with the older lens, and the slight improvement is enough to make this lens very competent. It was the other areas like the build, aperture, and focus motor that were higher priority needs, and Canon has addressed those.

Aperture Iris Improvement
Probably the best way to examine the update to the aperture iris is by viewing this video:

The video highlights a clear advantage for the new lens. The older version of the lens had 5 straight aperture blades that quickly began to produce a pentagonal shape in bokeh highlights. My feeling is that even by f/2.8 this look was somewhat cartoonish (not a fan of “creative apertures). The new lens has a vastly improved (modernized) aperture iris with 7 curved aperture blades. As a result the aperture stays quite round through about f/5.6, and only then does the shape of the blades become apparent. This is a huge improvement and addresses one of the fundamental flaws of the earlier lens. If you prefer to look at the crops themselves (and also have a look at how the SMC Takumar handles the same test, take a look at the full review here:

To summarize:

  1. Wide open the bokeh looks nearly identical to the older lens, which supports what Canon has said regarding a largely recycled optical formula.
  2. By f/2.8 the difference in the bokeh quality from the old lens to the two is extremely dramatic.  The roundness of the bokeh highlights on the STM lens is actually improved over the wide open look.
  3. The STM lens keeps largely round bokeh highlights through f/5.6, and while you can see the shape of the aperture blades then, the look is still pleasing.
  4. The Takumar lens has more blades (8), but they aren't as rounded.  It shows a hexagon shape even by f/2, though that shape is preferable to the pentagon shape of the older 50mm II.
  5. The Takumar bokeh has less of a hard edge towards the outer edges, resulting in softer looking bokeh in field use.

The overall quality of the bokeh character in the new STM is unchanged, though there is a vast improvement to the shape of bokeh highlights when the lens is stopped down. Overall bokeh quality is decent but unexceptional, with harder edges and less creamy softness of the better lenses.  Still, in field use the bokeh is far from displeasing in most settings:

Other Optical Observations
Chromatic aberrations are also noticeably more controlled. I am seeing very little chromatic aberrations in field use, and that is a big step up. The reduction of CA (probably through improved coatings) helps improve the bokeh quality, as bokeh highlights are frequent places where green or purple fringing show up. I have seen a bit of that at 100% magnification, but for the most part I’ve seen very little chromatic aberrations at all.

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It is clear the optical formula has been optimized, particularly when considers that they also managed to reduce the minimum focus distance from 1.5 ft to 1.1 ft while improving the maximum magnification from .15x to .21x. You can get a more thorough analysis/comparison as well as image crops in the full review.

Speaking of that closer focus distance: my findings are a mixed bag. Then lens does focus closer, but image quality at wide apertures near minimum focus doesn’t seem quite as good as less extreme distances. I’ve seen stronger performances near minimum focus than what this lens gives (like, for example, from the 40mm f/2.8). Still, I don’t think the lens is any worse than the previous version at minimum focus, and in my aperture comparison I noted a slightly better result for the newer lens.

Flare resistance is also dramatically improved due to Canon's new coatings on the lens. It will produce a few ghosting artifacts when the sun is in the frame, but the veiling is nearly gone and those artifacts are far less disruptive. It is subtle improvements like this that really make the lens a much better value.

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Distortion was already very low for field use, and that is unchanged here.  In field use the tiny amount of barrel distortion should be imperceptible.

Image quality overall is quite good for the money. It isn’t about to challenge the Otus or the Sigma ART, but it is a lot of lens at this price. There is still some haze at apertures wider than f/2.8 when you examine images at 100%, and color fidelity isn’t likely to threaten Zeiss anytime soon, but the images I’ve gotten from this lens are punching well above its bargain basement price. Stopping the lens down helps eliminate the haze and also extends the sharpness into the corners. At f/2.8 and beyond the image quality is impressive by any standard. This is great news for those of you that are looking to use the lens for general purpose work.

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Though modest, that little bit of optical improvement is going to be enough to make a lot of photographers happy. It also still leaves plenty of room for Canon to do something very impressive with their update to the 50mm f/1.4.

The Holy Grail…and Conclusions

The quest for the “Holy Grail” of 50mm lenses continues. I’ve yet to use one that really checks all the boxes for me. I am still looking for a 50mm lens with the attributes and size factor of the Canon EF 35mm f/2 IS. Namely, 1) Fast, accurate USM AF, 2) Excellent wide open sharpness, 3) A moderate size 4) Quality drawing and bokeh. IS (image stabilization) would be the icing on the cake. I’ve reviewed and used more than 17 50mm options, both modern and legacy, and none of them have quite hit the sweet spot for me. My hope is that Canon’s replacement for 50mm f/1.4 will be the lens I've been looking for.

But I’m spoiled by owning a large kit of excellent lenses and getting to constantly use the newest and the best as a lens reviewer. The target audience for this lens isn’t me; it is the millions of users who have a limited budget but want a competent wide aperture prime lens…and the EF 50mm f/1.8 STM is exactly that. It is hard to be critical when Canon has updated a number of key areas of this lens while leaving the price at a bargain basement level (only $125 in the United States). The “nifty fifty” was already one of the best values in photography; the new lens raises the value even higher. It is pretty much better in every area while remaining the exact same price.  Kudos to Canon for giving us so much for so little!

Should I Upgrade?
Expect the used market to become pretty flooded with the MKII version of the lens as, for a lot of people, the answer will be yes. If you are happy with what you have already, then know that optically there isn’t a big change. If you have issues with the aperture shape or want to shoot video and need quieter, smoother focus, then the answer is a big yes. If you’ve not yet purchased and want a cheap prime for portrait work or general purpose shooting, then this is an easy choice. It’s not that it is exceptional at anything, but it is good enough at everything that most users will be satisfied.

If you don't mind manual focus, consider picking up an SMC Takumar 50mm f/1.4 off the used market.  The 40mm f/2.8 pancake remains a solid alternative as well with an even more compact size, still better build quality, and great sharpness wide open.

Finally, if you are shooting a crop sensor body and want a higher grade of lens, I would recommend taking a look at the EF 35mm f/2 IS.  It is a bit larger, but still very portable, and on a crop sensor body it has a focal length equivalent of 56mm – right in the middle of “normal” range.  Its optical performance is exceptional, and the IS works very well, allowing extreme handholding.  It will remain one your favorite lenses even if you switch to full frame in the future.

If you do have an older EF 50mm f/1.8 II and are considering upgrading, I would move quick.  I fully expect the value on the used market to drop a bit.  Supply and demand…and there is about to be a lot of supply and not much demand.  At $125, the EF 50mm f/1.8 STM is a lot of lens!

Purchase Options:


  • Amazing value for the money
  • Improved build quality, including a metal bayonet mount.
  • Vastly improved aperture iris (modern design)
  • Autofocus quality and accuracy through STM
  • Slightly improved optical performance in key areas
  • Improved flare resistance, chromatic aberration control, and contrast
  • Improved minimum focus distance and maximum magnification


  • STM performance here slightly below the standard of other lenses
  • Optical improvement marginal
  • Manual focus with STM
  • Bokeh quality isn't exceptional