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Canon EF 40mm f/2.8 STM Lens Review

Gary Wolstenholme reviews the brand new pancake lens from Canon, the EF 40mm f/2.8 STM lens.

| Canon EF 40mm f/2.8 STM in Interchangeable Lenses

Handling and features

Canon EF 40mm f/2.8 STM Lens Review: Canon EF 40mm f/2.8 STM

The Canon EF 40mm f/2.8 STM is a slim, compact pancake type lens, which is compatible with Canon EF and EF-S camera bodies and costs around £230. A fast f/2.8 aperture should make this lens ideal for taking pictures in reasonably low light conditions and focusing is powered by Canon's new STM focusing motor.


Canon EF 40mm f/2.8 STM Handling and features

Despite being compact and lightweight, this lens is very solidly built. The lens barrel is constructed from high quality plastics and the lens mount is made of metal. When mounted on a camera, such as the Canon EOS 1Ds MkIII used for testing, the lens only protrudes from the body by around half an inch, which should make it the perfect companion for smaller full frame bodies, such as the EOS 5D series cameras, or even compact entry level models. Here the 1.6x crop factor will result in a field of view equivalent to a short telephoto 64mm lens.

Canon EF 40mm f/2.8 STM Lens Review: Canon EF 40mm f/2.8 STM

Autofocus is very swift and precise. A feint noise is made by the motor during focusing, which sounds not unlike what robots do in sci-fi films, but it is certainly quiet enough to cause very few issues. Unlike Canon's USM lenses, full time manual override is possible by keeping the shutter button half depressed whilst focusing, rather than just grabbing the focus ring at any time. A thin manual focus ring, which is damped just enough, provides control for this. A small switch on the side of the lens allows switching between manual and autofocus quickly.

Focusing isn't performed internally, but the 52mm filter thread doesn't rotate either, making this lens ideal for use with polarising and graduated filters.


Canon EF 40mm f/2.8 STM Performance

At maximum aperture, sharpness in the centre of the frame is already excellent, with clarity towards the edges approaching very good levels. Stopping the lens down improves sharpness across the frame, with clarity across the frame peaking at f/4.


Canon EF 40mm f/2.8 STM Lens Review: Resolution at 40mm
Resolution at 40mm

How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column.

The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple.

For this review, the lens was tested on a Canon EOS 1Ds Mark III using Imatest.

Chromatic aberrations are virtually non-existent, remaining under half a pixel width in size at all apertures. This extremely low level of CA, should pose no issues, even in large prints, or harsh crops from the edges of the frame.


Canon EF 40mm f/2.8 STM Lens Review: Chromatic Aberration at 40mm
Chromatic Aberration at 40mm

How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.

For this review, the lens was tested on a Canon EOS 1Ds Mark III using Imatest.

As is quite common for lenses of this type, falloff of illumination towards the corners is quite pronounced. At f/2.8 the corners of the frame are 2.1 stops darker than the image centre and visually uniform illumination isn't achieved until f/8.

Distortion is well controlled, with Imatest only detecting 0.5% barrelling. This low level of distortion should pose few issues for normal shooting. If absolutely straight lines are paramount, then you'll be glad to hear that the distortion pattern is uniform across the frame, which should make corrections relatively straightforward to apply.

No issues with flare were encountered during testing, with only a slight loss of contrast being noticeable when shooting directly into the light at wide apertures.

Canon EF 40mm f/2.8 STM Sample Photos


Value for Money

This lens is fairly unique for Canon cameras and the price of around £230 seems fair considering the optical performance. The Canon EF 40mm f/2.8 STM lens is available from Harrison Cameras.

Canon's EF 50mm f/1.8 lens may be a suitable alternative for those on a budget, especially as it weights about the same. Even though it isn't as compact or as well built as the 40mm lens, it is considerably cheaper at around £90 and has a maximum aperture over a stop faster.

Also, for around the same price, the Canon EF 50mm f/2.5 Macro lens can be picked up. Although this lens is a little bulkier than this 40mm optic, it does allow close focusing and 1:2 magnification.


Canon EF 40mm f/2.8 STM Verdict

Pancake lenses seem to becoming somewhat fashionable at the moment, due to their small size. Whether having a slim lens is that beneficial on a full size SLR body is open to debate, but at least the optical performance of this lens alone, makes it well worthy of consideration.


Canon EF 40mm f/2.8 STM Pros

Excellent sharpness
Low distortion
Compact and lightweight
Fast focusing


Canon EF 40mm f/2.8 STM Cons

No full time manual focus override
Strong vignetting
More than double the price of the 50mm f/1.8 (although performance and build probably justify this)



Canon EF 40mm f/2.8 STM Specifications

Lens Mounts
  • Canon EF
Focal Length40mm
Angle of ViewNo Data
Max Aperturef/2.8
Min Aperturef/22
Filter Size52mm
35mm equivalentNo Data
Internal focusingNo Data
Maximum magnificationNo Data
Min FocusNo Data
Box Contents
Box ContentsNo Data

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absolutic Avatar
19 Jun 2012 7:38PM

It works different than with USM Canon lenses, that is why you did not discovered it. You need to half-press the shutter, and keep it half-pressed, and while keeping it half-pressed, you can roll that focus ring and it will give you manual override!!!!! The difference is with USM lenses, you don't have to press or half-press the shutter to get a manual override.
theorderingone Avatar
theorderingone 19 2.4k
20 Jun 2012 11:47AM
No need to shout sir. Wink

Yes, we seem to have gotten a bit muddled in the very short time we had the lens for testing. We'll get that point amended.
IndigoRaven Avatar
20 Jun 2012 12:36PM
Wonderful to see another review on this new lens! Thank you for the charts and sample photos, now I know it peaks at f4 performance wise. Smile

Another justification to get 40mm/2.8 over 50mm/1.8 is smoother bokeh with 40mm due to 7 aperture blades, as 50mm has only 5. I am looking forward to acquiring Canon's 40mm in addition to 50mm I already have for the smoother bokeh alone.

I wonder when Canon will release in-camera lens correction update for the 40mm pancake... assuming one isn't already available...
jjkc_9000 Avatar
21 Jun 2012 10:05PM
it would seam to me that the rather better made 50/1.4 (that i regard highly) would be better compared to such a lens that 50/1.8 - which though very very sharp when stopped down to f/5.6-8 is not well built or good to focus by any method. I look forward to having a play with the 40/2.8!
banehawi Avatar
banehawi Plus
19 3.0k 4384 Canada
22 Sep 2014 8:15PM
This is simply the best value you can get in a super sharp Canon lens.

Its tiny; its very light; it looks like you dont have a lens on at all, its more like a lens cap; and, its fast, bright, and sharp.

I have the 50mm 1.4, and its rarely out of the box these days, = this 40mm lives on my 6D most of the time. Great on a full frame for street shots.

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