Canon EF 40mm f/2.8 STM “PANCAKE” Lens Review

When I first saw the pancake lens I was amazed of how small it is. It is the size and looks that had me wanting this lens. Of course, I shouldn’t forget to mention the price factor, because this lens is pretty cheap. You can get one for about $150.

EF 40mm 2.8 STM
EF 40mm f/2.8 STM


Focal Length & Maximum Aperture 40mm, 1:2.8
Lens Construction 6 elements in 4 groups
Diagonal Angle of View 57°30′
Focus Adjustment Inner Focusing System
Closest Focusing Distance 0.98 ft./0.3m
Filter Size 52mm
Max. Diameter x Length, Weight 2.7 x 0.9 inch, 4.6 oz. / 68.2 x 22.8mm, 130g

Size and feel

It looks ridiculously small once you put it on an DSLR, but that is the cool part, because your D-SLR suddenly becomes compact and light in weight. With this setup, I can walk around for hours with no need to shift my shoulders which I usually do when shooting with lenses like the much heavier EF 16-35 f/2.8. It has a quality feel and it seems pretty well built — way better than the plastic 50mm f/1.8 II for example. In the image below, you can see the size of the pancake lens compared to EF 50mm f/1.8 and EF-S 18-55 mm f/3.5-5.6 — all attached to the Canon EOS 550D (Rebel T2i).

EF 40mm 2.8 STM
Size matters ?

Focusing with STM (Stepping motor)

Its only downside when it comes to taking pictures is its auto-focus (AF) system. The EF 40mm f/2.8 uses a special AF motor called STM (stepping motor) which is intended for use while shooting videos. The manual focus will not work when the camera is off, because it’s not mechanically connected — you can turn the focusing ring as much as you like, but nothing will happen.

Once the camera is on and you’re manually focusing, the ring works very smoothly, and an exact focus point is easy to find. There is a slight delay in lens movement when you move the focus ring: the speed at which the lens moves isn’t directly related to how much you turn the focus ring. The focus system produces noise similar to that of compact cameras when their inbuilt zoom lenses extend. This may be an issue when using manual focus while making video with internal sound recording, but if you operate the manual focus slower, you can completely eliminate the noise. If you wish to use auto-focus in video mode (assuming your camera can shoot video), the EF 40mm f/2.8 will perform great. In my opinion, the pancake lens produces less  jerky and choppy videos in auto-focus mode than it’s rivals — even  outperforming lenses such as the EF 16-35 f/2.8 II. So it seems that this auto-focus system gets along with video much better than USM motors, not to mention that it’s quieter and fast.

However, when taking pictures, the auto-focus is not so fast. Once it’s off focus, it has a bit of time-lag in refocusing, so don’t expect it to have L series speed especially considering its price tag. The focusing problem is also present when taking pictures in low light conditions, in which the lens hunts for a focus point. But all the focus speed and noise issues have nothing to do with the accuracy of the auto-focus!

40 vs 50 vs 16-35
40 mm f/2.8 vs 50 mm f/1.8 vs 16-35 mm f/2.8 II L

The pancake lens’ focusing accuracy is consistent, regardless what your subject is. The AF accuracy of the EF 50mm f/1.8 cannot compare to the pancake’s. The 50mm f/1.8 may work when you need to focus in a controlled portrait shoot, but anything else is pure lottery.


Before we discuss Lens Sharpness anymore, you may want to read an amazing article about it here. To make a long story short, you should know more about how to use your gear before demanding any features from the gear.

What about sharpness? Well let’s just say I didn’t even bother moving it from f/2.8. It’s stuck there from the beginning because it’s just so super sharp even when wide open. I didn’t check any comparison charts or laboratory research reports on how sharp it really is, but I can say that from my own perspective: I’m extremely satisfied.

40mm STM Pancake
MTF Chart 40mm STM – 50mm f/1.8 II and 50mm f/1.4

Below, you can see a comparison which we’ve made using the EF 50mm f/1.8 II and the EF 16-35 f/2.8 II L lenses as rivals to the little pancake. The EF 40mm performed superbly even wide open by beating the 50mm even when its aperture was at f/2.8.

40mm f2.8 vs 50mm f1.8
40mm f/2.8 vs 50mm f1.8
40mm f2.8 vs 50mm f1.8
40mm  f/2.8 vs 50mm f/1.8
40mm f2.8 vs 50mm f1.8
40mm f2.8 vs 50mm f1.8
EF 40mm f2.8 vs EF 50mm f1.8
40mm f2.8 vs 50mm f1.8


We’ve used an expensive wide-zoom lens, the EF 16-35 f/2.8 II L, and set it to a focal length of 35mm, just to see how much does it differs from EF 40mm f/2.8 in wideness and sharpness. You can check the results below.

40mm f2.8 vs 16-35mm f2.8 II L
40mm f/2.8 vs 16-35mm f/2.8 II L
40mm f2.8 vs 16-35mm f2.8 II L
40mm f/2.8 vs 16-35mm f/2.8 II L
40mm f2.8 vs 16-35mm f2.8 II L
40mm f/2.8 vs 16-35mm f/2.8 II L
40mm f2.8 vs 16-35mm f2.8 II L
40mm f/2.8 vs 16-35mm f/2.8 II L


Conclusion: The little pancake lens is sharper throughout the frame, especially in the corners where both 50mm 1.8 and 16-35 2.8 start to fade.


All around lens:

Due to its size, the pancake lens is easy to carry around. On a full-frame (FF) body it captures a relatively wide field of view.


If the 50mm  f/1.8 is good for portraits, then the 40mm f/2.8 is even better. You have little bit more field of view (FOV), but you can easily crop if you need to.


With the new STM motor, it should be one of the best lenses for videos. It is better than most of the lenses in video mode, but in our opinion, until something changes, it is just not yet there.

We made some sample video shots, we will update article and place video here.


PROS: light, small, metal mount, precise focus, built quality, great for portraits and travel, fast when using AF feature while recording video (if you ever wish to do that)
CONS: slow focus, focus noise, takes some time to get used to working with STM, you need power to focus, even if camera or lens goes to sleep mode, you need to wake it up before focusing.


Some examples of photos taken with EF 40mm f/2.8:
40mm STM 3 Primo

Street Credibility Sean's Portrait


When having an EF 16-35 f/2.8 II and EF 50 f/1.8 II, one may say that buying a 40mm f/2.8 lens would be a waste of money, especially with the 50mm lens being much faster with its lowest  f-stop of 1.8. There’s a kernel of truth somewhere, but the EF 40mm f/2.8 is smaller, lighter, more precise, better built and sharper then most of its rivals. I would choose EF 40mm f/2.8 over 50mm f/1.8 anytime! I would definitely recommend it as a lightweight low-profile lens that can easily find a place in a photo bag, or even in your pocket.

Best places to buy your new Canon EF 40mm f/2.8 STM “Pancake” Lens:
B&H Photo

*Price at the moment is around $200 and with rebate around $150


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