Canon EF 40mm f/2.8 STM: Ahead of its Time

Canon EF 40mm f/2.8 STM

Canon EF 40mm f/2.8 STM

The Canon EF 40mm f/2.8 STM has some new technology that will cater to video enthusiasts, but what’s the stills quality like? Shridhar Kunte checks.

When Canon launched the EOS 650D in 2012, the company launched two STM lenses along with it. With the increasing importance given to video, the company felt that older technologies like USM were not able to do full justice to continuous autofocus during video capture and while shooting with Live View. And thus was born STM— lenses that have a stepping motor inside, to ensure smooth and silent autofocus.

Besides being the first STM lens, this is also Canon’s first pancake lens in the EF series. This makes it the smallest lens in the entire lineup! It is also the lightest, though the Canon EF 50mm f/1.8 is also equally lightweight (130g).

Popularly, it is believed that 50mm is a normal focal length, but technically, a normal lens is one whose focal length is closest to the diagonal of a sensor. In the case of a full frame sensor, this is around 42–43mm, which is why the 40mm f/2.8 is actually closest to it.

The lens’ elements are coated with a special Super Spectra coat, which claims to improve colour consistency and reduced flare. There is a seven-bladed aperture diaphragm, which renders extremely attractive bokeh in the out-of-focus areas. While STM is ideal for video, Canon should have included stabilisation, even if it would have meant a slightly bigger lens.

For a majority of time, I used this lens on EOS 6D, as I was interested more in knowing the stills-shooting capabilities of the lens. The video capabilities were tested on a 70D. The lens is made up of polycarbonate and feels sturdy. Unlike Canon’s 50mm/f1.8 lens (which is largely plastic), the mount of this lens is made of stainless steel.

The hood is not provided with the lens. If you buy it separately, keep in mind that it is attached to the filter thread. This basically means that it cannot be reverse mounted, so when the hood is not in use, you need to keep it separately.

Because of the internal focusing, the front element of the lens does not rotate. This makes easy to use a circular polariser. Interestingly, the manual focusing is done by the fly-by-wire method—a technology often found in mirrorless cameras, but are seeing for the first time in a Canon EF lens. This means that if the camera’s power is off, you cannot adjust focus and prefocus the lens. The focusing ring is tiny with a knurled finish and can be rotated very easily.

The AF speed is faster and quieter than the Canon 50mm/F1.8 lens. But when you compare the focusing speed and noise with 50mm/f1.4 lens, you will realise that the 50mm/f1.4 lens is superior in both these parameters. STM technology ensures quiet focusing in video, but in stills shooting, it is not completely silent.

It exhibits good centre sharpness through the aperture range. The best overall results I got when using the lens, was at f/5.6. Wide open, there is quite a bit of vignetting, but it diminishes when you stop down to f/4. There is a tiny amount of barrel distortion, but it is barely a bother in the real world. Chromatic aberrations are superbly control. AF in video is fantastic, but only when used with the new 70D.

At the end of the review, I was a little confused. Canon has put an attractive price tag of Rs. 9995 for this lens. But if you need a value-for-money lens for still photography, the 50mm f/1.8 is even cheaper. The build quality of this 40mm is better, but 50mm has a faster aperture and is equally lightweight.

Of course, this is a fantastic lens for someone who shoots both stills and video, but the catch over there is… the only camera that really uses the video capability of this lens is the 70D. And though this is a full frame lens, there is no Canon full frame camera that can get the video AF advantage that this lens offers! So curiously, one can say that the 40mm f/2.8 STM is a fantastic value buy, but only if you use a camera that can take advantage of its STM capabilities. Clearly ahead of its time!

This tiny pancake, when mounted on a small body like the 100D or the full frame 6D is great for street shooting. Exposure: 1/125sec at f/5.6 (ISO 4000). Photograph/Shridhar Kunte

This tiny pancake, when mounted on a small body like the 100D or the full frame 6D is great for street shooting. Exposure: 1/125sec at f/5.6 (ISO 4000). Photograph/Shridhar Kunte

Final Ratings
Pancake size, fulltime MF, no IS

Excellent sharpness, good bokeh

Build Quality
Metal mount, engineering plastic outer shell

Small MF ring, no distance scale

Warranty & Support
Two-year warranty, wide service network

Value For Money: 4/5

Who should buy it?
Street photographers and video enthusiasts who own a 70D.

The STM capabilities work magic while shooting video, but only on the latest 70D. In terms of stills, you lose f/1.8, but get a solid performer for a good price.

Tags: Shridhar Kunte, Lens review, Canon Lenses, October 2013, better photography reviews, Canon EF 40mm f/2.8 STM review, Canon EF 40mm f/2.8 STM, Canon EF 40mm f/2.8 STM price, canon pancake lens