Introduction

Ease of Use

The Canon EF 40mm f/2.8 STM lens

The Canon EF 40mm f/2.8 STM lens

The Canon EF 40mm f/2.8 STM lens

Weighing a mere 130g and measuring 22.8cm in length, the Canon EF 40mm f/2.8 STM is one of the tiniest lenses that Canon offers. You can use it on a Canon EOS APS-C body like the 700D that we tested it with for a short-telephoto 64mm equivalent angle of view, and it also balances well on a full-frame camera like the EOS 6D, providing a more "normal" field of view.

Side of the Canon EF 40mm f/2.8 STM lens

Side of the Canon EF 40mm f/2.8 STM lens

Top of the Canon EF 40mm f/2.8 STM lens

As you would expect from such an inexpensive lens, build quality is good rather than outstanding. The Canon EF 40mm f/2.8 STM feels solid in your hand, despite the all-plastic construction, with a metal mount adding to the solidity. The focusing ring is very narrow but has a ridged, rubberised grip band that assists with the finger-tip operation.

Front of the Canon EF 40mm f/2.8 STM lens

Front of the Canon EF 40mm f/2.8 STM lens

Rear of the Canon EF 40mm f/2.8 STM lens

The only other control on the lens barrel is a focus mode switch with the usual AF/MF settings. Note that this lens offers full-time manual focusing even when AF is selected.

Front of the Canon EF 40mm f/2.8 STM lens

Rear of the Canon EF 40mm f/2.8 STM lens

The Canon EF 40mm f/2.8 STM lens in-hand

The lens doesn't ship with either a lens hood or a protective bag. It accepts 52mm filters.

Focal Range

At the 40mm focal length the angle of view is 57°30'.

 Field of view at 40mm

Focusing

Given its tiny size, the Canon EF 40mm f/2.8 STM lens understandably has a very narrow focusing ring. Manual focusing is of the electronically-driven, 'focus-by-wire' type, more typically found on compact system cameras. There are no hard stops at either ends of the range, making it more difficult to set focus at infinity. Polariser users should be pleased that the 52mm filter thread doesn't rotate on focus.

When it comes to auto-focusing, the Canon EF 40mm f/2.8 STM zoom is a fairly slow performer, taking about 0.3 seconds to lock onto the subject when mounted on the Canon EOS 700D that we tested it with.

We didn't experience too much "hunting" though, either in good or bad light, with the lens accurately focusing almost all of the time. It's also a quiet performer, thanks to the built-in STM (Stepping Motor), which makes this lens well-suited to video recording.

Chromatic Aberrations

Chromatic aberrations, typically seen as purple or blue fringes along contrasty edges, are impressively well controlled with this lens - the examples below show the worst-case scenario.

Light Fall-off

With the lens wide open at f/2.8, you can't really see any light fall-off in the corners, and distortion is also very well controlled.

Macro

The Canon EF 40mm f/2.8 STM is not really a macro lens, but the close-focus point is a useful 30cm from the film/sensor plane, and Canon quotes a maximum reproduction ratio of 0.18x for the lens. The following example illustrates how close you can get to the subject, in this case a CompactFlash card.

Close-up performance

Bokeh

Bokeh is a word used for the out-of-focus areas of a photograph, and is usually described in qualitative terms, such as smooth / creamy / harsh etc. One of the reasons to buy a fast lens is to be able to isolate the subject from the background, and the Canon EF 40mm f/2.8 STM has an iris diaphragm with 7 rounded blades for a pleasing rendering of the out-of-focus highlights. Below you'll find some examples, but you are also encouraged to check out our sample images.

Sharpness

In order to show you how sharp this lens is, we are providing 100% crops on the following page.