Canon's mirrorless system has a small, but growing, library of lenses. The EF-M 18-150mm f/3.5-6.3 IS STM ($499.99) is an attractive option for photographers who want an all-in-one solution, as it has a long zoom range and a compact design that matches well with EOS M bodies. It makes some of the optical compromises you expect from a lens with a big zoom ratio, including a narrow maximum aperture, and soft edges and some barrel distortion at 18mm, but is a fine example of what a long zoom mirrorless lens can be. It's worth adding to your kit if you use the Canon system and want an all-in-one zoom.

Design

The EF-M 18-150mm covers a long range, but measures in at 3.4 by 2.4 inches (HD), weighs just 10.6 ounces, and supports 55mm front filters. Its weight is controlled via liberal use of plastic, including the lens mount, but the 18-150mm doesn't feel cheap. It's available in a graphite black or silver finish. Front and rear caps are included, but not a hood.

The lens does extend when zoomed. The zoom action is controlled by a ring that occupies the bulk of the barrel. It's marked at 18, 24, 35, 50, 70, 100, and 150mm. There's a smaller ring at the front of the lens that adjusts manual focus. The lens includes image stabilization, and its autofocus system is powered by an STM motor that delivers smooth, silent focus when shooting video.

The EOS M system is built around the APS-C sensor size, so the lens covers a range that's equal to a 28.8-240mm lens mounted to a full-frame camera system. Coverage isn't as wide as you get with the system's current kit lens, the EF-M 15-45mm, but the telephoto reach is much greater.

Minimum focus distance varies based on the focal length. It can lock on to subjects as close as 9.8 inches (25cm) at focal lengths wider than 50mm. The distance extends as you zoom, settling in at 17.8 inches (45cm) at 150mm. That's good enough to capture images at about one-third life-size, giving the zoom a pretty decent macro capability. If you want to focus closer, consider a dedicated macro lens like the EF-M 28mm, which can magnify images at up to 1.2 times life-size.

Image Quality

I tested the EF-M 18-150mm along with the 24MP EOS M6. At 18mm f/3.5 the lens scores 2,392 lines per picture height on Imatest's standard center-weighted sharpness test. Detail is very crisp at the center, topping 2,800 lines. There's a drop as you move away—the mid parts show about 2,183 lines, which is still better than the 1,800 lines we want to see at a minimum, but edges are on the soft side at 1,690 lines.

There's modest improvement to the average score as you stop down—2,433 lines at f/4 and 2,488 lines at f/5.6, but not any real noticeable improvement at mid parts and edges of the frame. Diffraction cuts into resolution as you stop down further, dropping the score to a still strong 2,280 lines at f/8. At f/11 we see some real improvement at the edges (2,029 lines), even though the average score drops to 2,248 lines—it's the f-stop you want to use for landscape shots. Avoid f/16 (2,036 lines) and f/22 (1,551 lines), as there's no real advantage to setting the aperture that small.

See How We Test Digital Cameras

Image quality is stronger at the edges at 35mm. At f/5 it scores 2,283 lines, with edges that are nearly as crisp as the average (2,055 lines). There is a slight improvement in resolution at f/5.6 (2,320 lines) and f/8 (2,349 lines). Quality takes a slight hit at f/11 (2,275 lines), and a more noticeable one at f/16 (2,103 lines) and f/22 (1,640 lines).

At 70mm the maximum aperture has dropped all the way to f/6.3, limiting usefulness in dim light. It scores 2,553 lines there, with strong performance from edge to edge. Scores drop a bit as you stop down to f/8 (2,449 lines) and f/11 (2,307 lines), and more so at f/16 (2,097 lines) and f/22 (1,665 lines).

Photos are still crisp at 150mm, although the very center isn't as detailed as you get at 18mm. The lens manages 2,073 lines at f/6.3, with image quality that's roughly the same from edge to edge. You get a bit more resolving power at f/8 (2,106 lines) and f/11 (2,258 lines). We see the expected drop in quality at f/16 (2,015 lines) and f/22 (1,599 lines).

You do have to deal with some distortion when shooting with the 18-150mm. Shooting at 18mm introduces strong barrel distortion, 4.4 percent, which renders images with a noticeable outward curve. Zooming to 35mm gets rid of the barrel effect, but introduces about 1 percent of pincushion distortion—straight horizontal lines in images appear to curve inward toward the center. It increases to about 1.2 percent at 70mm and settles in at 0.8 percent at 150mm. Unfortunately, the EOS M6 and other cameras in the system don't support automatic distortion correction, so you'll need some image editing tools to remove it, even when shooting JPGs,

Peripheral illumination—the effect of dimmed corners in images—is able to be automatically corrected for JPG shooters. If you leave illumination correction turned on and shoot JPGs, images are evenly lit throughout the zoom range. Raw photographers will have to contend with corners that are noticeably dimmer than the center at wide angles. At 18mm you get -3EV at f/3.5, -2.7EV at f/4, and -1.5EV at f/5.6; at narrower f-stops the effect is kept under -1EV. At the other focal lengths we tested, 35mm, 70mm, and 150mm, the corners are within -1EV at every f-stop.

Conclusions

There are unavoidable compromises required to keep a lens reasonably sized and priced, while at the same time offering a long zoom range and covering an APS-C image sensor. The Canon EF-M 18-150mm f/3.5-6.3 IS STM sacrifices some light-gathering capability, shows some barrel distortion, and doesn't have the sharpest edges at 18mm, but aside from that is a very solid performer, delivering crisp images and including image stabilization. If you're invested in the EOS M mirrorless system and want a lens that covers a long range so you won't have to deal with swapping it out for another frequently, the 18-150mm is a solid choice.

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