OM System (formerly Olympus) cameras are a popular choice for photographers who work outside the studio. The Micro Four Thirds sensor format allows for lightweight lens optics that are easier to carry than heftier full-frame glass. The M.Zuiko Digital ED 40-150mm F4.0 Pro ($899.99) is a perfect example—it's a diminutive zoom with telephoto reach and an all-weather construction. Pros should likely stick with the exceptional M.Zuiko ED 40-150mm F2.8 Pro ($1,499.99), but the more affordable ED 40-150mm F4.0 Pro is a worthwhile option for enthusiasts, and an Editors' Choice winner in its own right.

Retractable Optics, With Internal Zoom

The 40-150mm F4.0 is quite compact, especially when you consider its equivalent full-frame reach (80-300mm). It measures just 3.9 by 2.7 inches (HD), but uses a retracting design to accomplish the feat—you have to twist the zoom ring with a little torque to extend (or retract) the optics. The lens is about 1.2 inches taller when it's extended and ready to use. The zoom action itself is internal, however, so there's no in-or-out movement when you adjust the focal length.

We reviewed the larger 40-150mm F2.8 Pro more than a few years ago—it stood out in 2014 and remains on sale today. That lens covers the same focal range, but gathers twice as much light—if you're using a Micro Four Thirds camera to photograph sports indoors or at night under stadium lights, the F2.8 zoom is the better choice. But in addition to a higher $1,500 price, it's also bigger all around (about 6.3 by 3.1 inches) and heavier (1.7 pounds versus 13.5 ounces for the F4.0).

A couple of other differences are notable. Unlike the F2.8, the M.Zuiko 40-150mm F4.0 doesn't work with teleconverters. The smaller lens also drops the mechanical manual focus clutch, and the manual focus-by-wire is comparatively lacking. You won't notice those last two changes if you rely on autofocus, however.

The F4.0's build is topflight. The outer barrel, zoom ring, and focus ring all feature a metal finish, and the inner barrel, front element, and hood also mix in some polycarbonate. The lens matches the OM-1 camera's IP53 rating, so neither dust nor splashes should be an issue.

The front glass sports an anti-smudge fluorine coating, something we appreciate on lenses. The coating makes the lens easy to clean—just keep a microfiber cloth handy—and beads away water drops. You can also add a protective filter; the lens uses the 62mm size.

Handling and Focus

The M.Zuiko 40-150mm's retractable design makes it handle a little bit differently than typical zooms; you need to twist the zoom ring before taking a photo. It's not a big deal, though—there's no locking switch to fumble with—and I like the option to close down the lens for storage in a smaller bag.

The zoom ring has a metal finish with textured ridges for a ready grip and takes up most of the room on the barrel. The narrower manual focus ring is just ahead; it also uses a metal finish, but has a slightly different texture to set it apart from the zoom control. Focus control is electronic, but the control ring does have some resistance, a necessary bit of tactile feedback.

We expect most photographers to lean on autofocus. The 40-150mm F4.0 focuses quickly (but not instantly) when paired with the OM-1, snapping from a close to a distant subject with just a slight hesitation. This brief hesitation isn't something that caused me to miss any photos in practice, but it does mean the lens is limited to 25fps continuous focus with the OM-1.

Videographers can use autofocus, too—the focus motor is practically silent. Manual focus is also an option, though the nonlinear response means you can't set marks to hit focus racks perfectly. That's a bit disappointing, because the lens is otherwise particularly suitable for rack focus shots—we didn't notice any change in angle when setting focus, also known as the focus breathing effect.

OM opted to leave stabilization out of this lens, putting the task on the camera body instead. With the OM-1 that's not a serious concern—I snapped sharp 1/8-second handheld images consistently at the 150mm focal setting and a few good ones at 1/4-second, too. There is one downside—you still see the effects of handshake in the viewfinder when you're setting up your photo. It's a minor concern in practice—the IBIS system kicks in and smooths out your view as soon as you engage the autofocus.

Focus is available to 27.6 inches, good enough for 1:2.4 macro results. The autofocus can hunt a little when you work at close distances, though. OM System opted to not include a focus limiter switch on the lens or add an L-Fn button on the barrel. These omissions take away some of the lens' appeal, but undoubtedly make it a little easier to protect from the elements.

M.Zuiko 40-150mm F4.0 Pro: In the Lab

I paired the 40-150mm F4.0 with the OM-1 camera and Imatest software to check its optical performance in the lab. Resolution is outstanding at 40mm (2,900 lines), and at the top of our excellent scale for a 20MP sensor at 100mm and 150mm (2,700 lines). Results are sharp with the lens wide open at f/4, and you can use it comfortably down to f/11 with no loss in quality. Diffraction limits detail at f/16 and f/22, the same as with any lens on a Micro Four Thirds system camera.

In-camera corrections remove distortion from JPGs, and Adobe Lightroom already has a profile to correct Raw shots. If you use a different processor, you might see some pincushion distortion when you zoom in, but that's pretty easy to remove.

Micro Four Thirds cameras don't blur backgrounds as effortlessly as full-frame models, but can still produce images with the bokeh effect. The 40-150mm does a good job here, smoothing out busy backgrounds and drawing clean, mostly circular highlights—though you still get the cat's eye effect toward the edges of the frame at wide-open apertures. Stopping down to f/5.6 or f/8 rounds them out.

A Take-Anywhere Telezoom

The OM System M.Zuiko Digital ED 40-150mm F4.0 Pro is a thoughtful addition to the Micro Four Thirds system and, as far as telezooms go, is a real Goldilocks lens. It splits the difference between the high-end M.Zuiko 40-150mm F2.8 Pro and the budget-priced M.Zuiko 40-150mm F4.0-5.6 R, a $200 option that's simply not in the same league.

We see a lot of appeal in this midrange offering. At $900, the 40-150mm F4.0 Pro isn't inexpensive, but the price is reasonable for photo enthusiasts who buy dedicated cameras—the general public is happy with smartphone snaps. This F4.0 telezoom delivers strong value for the dollar, and is the one to get if you don't need an F2.8 aperture for low-light work, earning it our Editors' Choice award. Outdoor photographers should pay special attention to this lens, as it's easy to carry, can withstand the elements, and offers both close-up focus and telephoto reach, a great combination for nature work.