Canon EF-M 22mm f/2 STM

SLRgear Review
February 17, 2013
by Andrew Alexander

Canon announced its EOS-M mirrorless camera in July of 2012, and the EF-M 22mm ƒ/2 STM was one of two lenses to be released with it.

The 22mm ƒ/2 was designed specifically for the EF-M lens mount, and is incompatible with other Canon bodies. The EF-M mount is designed around an APS-C sensor: in 35mm film terms, the effective field of view is approximately 35mm. Be sure to check out our review of the EOS-M at Imaging Resource.

The lens does not ship with the EW-43 lens hood - this is an optional accessory that retails for around $25. The lens itself is available now for around $250, or as part of a EOS-M camera kit.

Sharpness
The Canon EF-M 22mm ƒ/2 STM provided surprisingly sharp results. When used wide open at ƒ/2, there is some corner softness to speak of, but the majority of the frame is very sharp. Stopping down to just ƒ/2.8 provides very sharp images - for practical purposes, we would say it's tack-sharp from corner to corner. According to the raw numbers you'll have to stop down to ƒ/4 to see the sharpest results, but to the naked eye I doubt you would see the difference.

The lens is sharp all the way to ƒ/8, where diffraction limiting begins to set in, but there isn't a significant impact on sharpness until ƒ/11, and even then it's just a slightly overall decrease. Images start to lose their sharpness at ƒ/16, and become moderately soft at ƒ/22.

Chromatic Aberration
While our testing software gives the 22mm ƒ/2 a passing grade, we note some obvious chromatic aberration present in the extreme corners of the frame at the ƒ/2 setting (take a look at our sample images for further detail). In the center of the frame, it's not an issue. Stopped down to ƒ/8, it's less prominent but still visible in the corners: again, the center of the frame is fine.

Shading (''Vignetting'')
There is some significant corner shading with the 22mm ƒ/2: used at the ƒ/2 setting, the corners show up a full stop darker than the center of the frame. This is alleviated as the lens is stopped down, but at ƒ/4 and smaller there is still at least a half-stop of corner shading. It's worth noting that our still life shots (found in the sample images) are done with default settings, which means that the Peripheral Illumination is enabled, so you can see how the camera can correct for corner shading.

Distortion
The 22mm ƒ/2 provides excellent resistance to distortion (or, the EOS-M camera is doing some fine correction); there is no distortion to be had with the lens.

Autofocus Operation
Canon employs a STM motor on this lens, providing near silent operation. Unfortunately it's not especially speedy, taking well over a second to go through its range of focus.

Macro
The lens, while not specifically built for macro, offers some usable close-up capability. Maximum magnification is 0.21x, with a minimum close-focusing distance of around six inches.

Build Quality and Handling
The EF-M 22mm ƒ/2 STM lens is small and light (105 grams, 3.7 oz): it comes finished in a nice gray color. The small size of the lens allows you to put this lens and camera combination in a large coat pocket, providing you with a higher-quality point-and-shoot alternative.

The lens has seven elements in six groups, with one aspherical element, and has a rounded aperture with seven blades. There are no switches or control surfaces other than the manual focusing ring, so its simple design matches nicely with the EOS-M.

The focusing ring is a scant 1/8'' in width, plastic with a cross-hatched pattern for texture. The focusing design is electrical, so the ring will turn in either direction without stopping. There is a little bit of lens extension as the lens is focused: it will extend by around a quarter of an inch. The front element (and any attached 43mm filters) will not rotate during focusing operations.

The optional EW-43 lens hood is available for the lens, but does not look to provide a huge amount of shade for the lens.

Alternatives
There aren't a lot of alternatives at the time of writing, owing to the young age of the EF-M mount.

Canon EF-M 18-55mm ƒ/3.5-5.6 IS STM ~$300
We haven't yet tested this lens, but plan to do so in the near future.

Conclusion
For a small and relatively inexpensive lens, the Canon EF-M 22mm ƒ/2 STM provides an excellent result. Given the few options available (as of February 2013) for Canon EOS-M users, having this prime lens as an option is a no-brainer.

Product Photos

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.