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Canon 40mm Pancake – How Did They Do That??

Published June 21, 2012

We got our first batch of the Canon 40mm f/2.8 pancake lenses in today and, as with all new lenses, I had to run them through Imatest to establish our acceptable standards for the lens. Let me start by saying I had low expectations. I don’t particularly like pancake lenses except on tiny cameras. They’re usually compromises between size and image quality and I’m an image quality guy, mostly. And, come on, it’s a $200 lens. But duty calls, so test them I must.

My first impression was the build quality was better than I expected. It has a metal mount, not plastic. The aperture blades appear more curved than most of the Canon 7 blade aperture rings, making a more circular opening. The little STM motor is not silent, but it’s pretty quiet. It’s also not lightning fast (as expected) but autofocus is certainly quicker than a Canon 85mm f/1.2 lens. And it’s amazingly tiny — the rear lens cap is about half as big as the lens. So far, so good, if the image quality doesn’t suck too bad.

Imatest Results

As always, these are Imatest MTF 50 results, so they reflect the performance at about 12 feet distance in our lab. Infinity and close-up results could be different to some degree. But the little 40mm has amazingly good numbers. To give some perspective, I’ve put it in a table with results for some other f/2.8 lenses. The higher number is MTF 50 at the center point, the lower number is average across the entire lens front measured at 20 points.

 Lens  Center  20 pt
Canon 40mm f/2.8 870 775
Canon 24-70 740 610
Canon 16-35 770 635
Canon 45 TS-E 785 660


You can see the average number is really excellent, which is especially surprising since pancakes often have poor corners. This is sooo not the case here that I’ll show you a graphed printout of a typical copy. Notice it retains excellent sharpness right out to the absolute corners on a 5D II.


One thing I have to note: the results were VERY consistent. We only had a dozen copies to test but there was  little lens-to-lens variation. As a rule pancake lenses don’t have lots of optical calibration adjustments inside, so they may depend on the manufacturing tolerances of the housing more than most lenses. Take this with a bit of a grain of salt, though, all the copies we tested were close in serial number, so there could be more variation when we get another dozen copies.

The 40mm f/2.8 lens is near peak sharpness wide open. The graph below shows 8 copies I tested at both f/2.8 and f/5.6. There’s only a slight increase in sharpness (I’m not certain that difference would be visible in a photograph, it’s within 5 SQF points.) That’s wonderful, but I want to point out that a lot of lenses that do improve stopped down (like the 3 in the table above) would ending up being sharper than the 40mm at f/4 or f/5.6.

The only other comment I have about the little lens is that manually focusing, while possible, is rather difficult: the focusing ring is really thin and I found a fingernail moves it better than my whole fingertip. Mostly, though, it has a small range so a tiny movement can move the focus a lot. But then, one of the main purposes of this lens was to provide smooth video autofocusing.

Overall, though, I’m extremely impressed. I’d be impressed if a lens this size and price was just decent, but this one is excellent. I might as well go ahead and get in trouble with the business manager: if you think you want this lens, just go ahead and buy it. At this price, unless some of the more thorough reviewers find something I missed on this quick overview, you can’t go wrong.

Roger Cicala

June 2012

Author: Roger Cicala

I’m Roger and I am the founder of Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

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  • mrkgoo

    I’m also getting some issue where the motor will not engage after a period of sleep and requires remounting.

    Canon 7D.

  • Dan

    Thanks for the review. A usually forgotten factor is that cheap lenses use lower quality glass, and this affects color rendering very noticeably in some conditions. An example is the 50/1.8 vs 50/1.2. What about this lens ?

  • Vu

    Daniel: I noticed the same thing. I was able to duplicate issue every time by doing the following: when it’s working, focus at infinity (and the inner tube will be at the maximum extension). Turn off the camera. Put the cap on, and continue to press (albeit gently), so the extended tube is now retracted all the way in. Turn the camera on. Viola! The focus mechanism does NOT engage, even if you press shutter button half-way down. Nothing will engage the focusing again until you re-mount the lens again.

    Weird! And a bit discomforting, as you mentioned! It doesn’t take much effort to push that tube back in, and it’s been happening so often when I put the camera (with lens mounted) in my bag and run off to my next meeting, etc. I always have to re-mount the lens, and it takes away from having a camera ready at any moment.

    I’ve read all of Canon’s current manual and instructions included with the lens, and how the STM goes to sleep when it’s not being used, and how it gets it’s power from the camera, and that’s why it can’t be focused manually when it’s off, etc.

    I’m not sure if there’s a work-around at this point. This is a big issue for me, and I’m thinking of returning the lens because of it (unless there’s a workaround).

    Besides the obvious: “don’t push the tube back in,” “re-mount the lens every time,” I’m hoping someone has a suggestion so I can keep this otherwise nice lens! 🙂

  • Roger Cicala

    Hi Daniel,

    I haven’t taken one apart yet to see the insides, but that could be a gear with a broken tooth. I’d send it back to swap out if you can.


  • Daniel

    Focus already stopped working after one day.
    Worked again after remounting the lens.
    Not a good feeling though on the first day.
    Even for manual focus the motor is needed.
    Manual focus was disengaged as well?
    Broken or just a small hickup?

  • confused

    just purchased. why does the instruction manual only list EOS 1 series (+ EOS 3) under:
    About the AF frame selection:
    * High accuracy cross detection can be used in the center AF frame and horizontal line detection can be used in the frames other than the center AF frame for the following cameras (then goes on to only list 1D series cameras).

    Many more canon cameras have fast lens support for AF. Why are the 1D cameras the only ones called out? I personally am not sure how many 1D owners will buy this lens, although it’s probably the closest to a normal prime on the 1.3 body.

  • Jeff Jolie

    Thanks for the report. Just bought one, plan on using it in NYC this weekend!

  • Stefan

    @Peter Thomas: A 2x teleconverter will turn the lens into a 80/5.6. Doesn’t make too much sense, does it?

  • Brad Harris

    Do you think it’s a better lens than 50mm 1.8 or 1.4 for pure sharpness, particularly for art reproduction, products or group photos?

  • Any thoughts on the viability of popping on a 2x teleconverter to further benefit from a light and mobile kit?

  • Luke

    Question to owners
    In the movie mode: is it possible to focus the lens manually all the time or does it go into sleep mode (just like when shooting stills) and you have to half press shutter button to wake it up. Thanks.

  • Rob S

    I buyed this little gem two days ago, and it is excellent ! Some little color fringing at the edges. Also I see vignetting at full open, but never a problem. I will wait if Canon updating its DPP-software adding this lens. After that, fringing and vignetting will be completely solved ! Now I search also for a small bag to transport it on my 5DMKII !

  • ererere

    now imagine canon would update their 20 year old 50mm f1.4 lens with todays technology…. that would impress me but not a rather slow f2.8

  • Christian Armetta

    Roger, do you know if it is a Tessar design?

  • RP


    What about its video performance? Did you test it in video mode? How do you place it: A portrait or a landscape lens? You said its STM motor is not silent but quite quiet. Did you test it in the new Rebel T4i? You said your lens batch gave even results. Did you think that lens results tend to group around a serial batch?

  • Elias T

    Nice and detailed review! I just have one more question. I heard that manual focusing is only possible when the lens is attached to a camera that is switched on (does the lens actually fall into sleeping mode after a few seconds in manual mode and is that an issue?). If so, would the lens also work on an analog canon 1000f for example?

  • Roger Cicala

    Hi Eric,
    I’d put it about the same as the 18-55 IS kit lens / Canon 50 f/1.4 lens category. Not lightning, but it moves along well.

  • Rex Gigout

    I found one of these wonderful little lenses at a local big-name electronics store. (Camera dealers and on-line seelers still seemed to still be waiting for theirs.) At the low price point, I did not expect excellence, but the 40mm EF is a remarkably good lens, based upon what I am seeing on an IPad, which is the best monitor available to me at this point in time.

    2.8 is not as fast as some of my L primes, but I tend to stop them down a bit, anyway, unless I am shooting in darkness.

    For those who wonder about the wisdom of such a tiny lens on a bulky DSLR, well, I love the combination of this pancake on my 5D. Yes, a DSLR is indeed bulky, so why add a bulky lens? Instead of the expense and compromises of buying and
    using a compact system camera, I have made my 5D amazingly easier to tote, whether on a strap, or inside a much
    smaller bag or case. I predict this little lens may be less intimidating when out and about in public. I plan to try that tomorrow or this evening.

  • Chris Mac

    I sold my 50mm 1.4 today after using this 40mm for the past week. I know now that I will never put that glass on my 5D again and as I primarily use the fixed glass for street photography, this new pancake is the perfect discrete piece of glass.

    I was even looking into getting Voigtlander Ultron SL II 40mm f/2.0 which is marginally faster but it a pure manual focus lens. Great in theory but poor in practice because getting that last second shot just doesn’t happen when you have to focus.

    This is my new daily glass for my camera despite owning 24-70 and 70-200

  • Eric

    Roger, thanks for this. Here’s a question that will help me decide if this lens will focus fast enough for me to use to catch my daughter and son in action.

    Does this lens focus as fast as the nifty fifty? Does it focus as fast as Canon’s standard kit lens? These comparisons will really help me. Thanks.

  • John Fryatt

    @jack: “What’s the point of such a small lens on a bulky DSLR”
    @Nicholas: “an itty-bitty pancake on a 5D-sized brick seems a bit silly”

    The point is that it makes the body/lens combo (even a 5D) considerable easier to carry around, as it’s much flatter and therefore fits in a bag etc. a lot easier. Secondly, it is a lot less intimidating to people than a huge zoom stuck in their face.
    I have one of these lenses now. Haven’t had a chance to use it extensively yet, but first looks are very good. Focussing speed is quite satisfactory (particularly for the use it is likely to be put to) and I can’t see any of the vignetting some have mentioned.

  • About the bulk, what will be the overall depth from the filter rim to the LCD rim on a 5D MK II, compared to a Pentax K5 with its 40mm pancake? The flange to sensor distance of the Canons is already short compared to Pentax flange to sensor depth, the Antishake of the Pentax sensor must add some mms too.

  • Neil Kirby

    @jack: “What’s the point of such a small lens on a bulky DSLR”
    @Nicholas: “an itty-bitty pancake on a 5D-sized brick seems a bit silly”

    I think it’s a vacation lens when used on a full frame. (I could be wrong).

    Being wider than 50mm gives you better scenery shots. Any wider and your people shots would be too compromised. If you can only pack ONE lens, it might be the lens to pack when space and mass really count. When you have to carry the camera on your person by the neck strap (instead of in a bag), the tiny lens is less obtrusive, less conspicuous (no white body, no red ring), and less likely to get bashed.

    You might question using a 5D as a vacation camera, but with a f/2.8 lens it will stomp any point and shoot in low light situations. If you are on a vacation (as opposed to a photo shoot), then you want normal perspective with the highest quality you can easily get.

    I don’t see other killer uses – but this isn’t my favorite focal length.

  • Robin Smith

    Vignetting is not a problem – its a feature for most shots. It looks a good one. Not sure whether I need one over the 50s – without a hood they are quire small small too.

  • roger: thanks for the review.

    @jack: “What’s the point of such a small lens on a bulky DSLR!” – perhaps to minimize that very bulk? shoot one-handed on the fly? to use as a back-up lens on your back-up smaller body? to fill that tiny empty spot in your bag? to keep in your shirt pocket?

    @leonard: “such a rip off of Pentax” – didn’t pentax make the first slr? all the companies “ripping off” each other is what pushes the technology and allows us to enjoy their fruits!

  • Very nice at that price though bokeh and vignetting has to be checked too. The alternative Voigtländer 40mm or competition Pentax 40mm (APS) do not score well on bokeh and vignetting. Both have no STM motor aboard and their price is high. The bigger old Canon 35mm f2.0 is sharp and cheap but has the same bokeh and vignetting limitations. The bigger Zeiss 35mm f2.0 is in a different price category but is not free from vignetting too. All in all Canon marketing and the engineers aimed at a weak spot in the competition and succeeded even when bokeh and vignetting are like the other pancakes:

    Wonder what basic lens design pancakes like that fall within: Planar, Plasmat or a WA design?

  • I’ve been recommending people get the 50mm 1.8 as their first lens after the kit lens. I think I’d rather recommend this lens. The 50 is just a little too long on a crop camera. Sounds like it’s a great little lens. Thanks for the review!

  • Leonard

    such a rip off of Pentax

  • “The 40 is fairly unique in that it just doesn’t get much sharper stopped down”

    The Canon 28/2.8 is similar in this regard. See

  • Jack

    What’s the point of such a small lens on a bulky DSLR!

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