The OM System M.Zuiko Digital 17mm F1.8 II ($549.99) is the first update to the original M.Zuiko 17mm F1.8 from Olympus, a lens that wowed us on its release more than a decade ago and has established itself as a mainstay of the Micro Four Thirds system. The updated edition uses the same optical formula, so there's no difference in picture quality, but adds weather sealing so you can be more confident using it in inclement conditions. The weather protection comes with a design compromise: The handy manual focus clutch from the original is no longer included. The 17mm F1.8 II is a good lens to get if you prioritize size and weather protection, and, like the first edition, earns our Editors' Choice award for Micro Four Thirds primes around this focal length.

Design: A Short Stack of Pancakes

There's no hard and fast definition of a pancake lens, but the general idea is that it's one that doesn't jut out beyond the height of a typical camera grip. The M.Zuiko 17mm F1.8 II doesn't quite make that grade but falls into a category of small primes that I like to describe as a short stack. Quantitatively, that's 1.5 by 2.3 inches (HD) with a featherweight 4.0-ounce carry weight and support for the same 46mm filter size used by similar lenses with other focal lengths, including the M.Zuiko 12mm F2.0 and the 25mm F1.8 II, so you have options if you would like a wide- or standard-angle lens instead.

(Credit: Jim Fisher)

The lens sees a moderately wide angle of view, roughly the same as a full-frame camera with a 35mm lens attached, but at a slightly boxier 4:3 aspect ratio that gives Micro Four Thirds its name. It's not quite as wide as the 3:2 sensors used in APS-C and full-frame systems, but comfortable for older photogs who cut their teeth on a 645 medium format system. The 35mm-equivalent focal length is a popular one for many types of images, including family snaps and candids, documentary and street photography, and general slice-of-life imaging. If you prefer a slightly wider angle, consider the Lumix G 15mm F1.7, a similarly small, metal-barrel prime from Panasonic, or look at the pricier M.Zuiko 20mm F1.4 Pro for a prime with just slightly narrower coverage for more subject isolation.

(Credit: Jim Fisher)

Cameras from OM System (and Olympus before it) have a proven track record of excellent weather resistance, but sealing is only good as its weakest point, and the original edition of the 17mm F1.8 did not incorporate gaskets to discourage dust and moisture ingress. This mark II version includes it and is rated for IPX1 drip protection when paired with a sealed body. As for durability, the barrel is aluminum, like the original, with a black anodized finish. To compare, similar lenses like the Sigma 16mm F1.4 DC DN Contemporary and the Panasonic Lumix G 15mm F1.7 aren't fully weather-sealed.

(Credit: Jim Fisher)

The lens ships with front and rear caps, as well as a reversible plastic lens hood. The hood adds a little depth to the M.Zuiko 17mm, detracting from its twee nature, though it's worth using as it adds some extra flare resistance and protection for the front glass. The front element omits anti-smudge fluorine protection, so you'll want to use the hood to stop water marks from forming due to raindrops or to avoid an accidental fingerprint smudge on the glass.

Handling and Focus: Fast Focus, Few Controls

The 17mm F1.8 II only has one control surface, its manual focus ring. The knurled metal ring is easy to find by touch as it makes up the bulk of the exterior. Manual focus aficionados should take caution, however, as the 17mm II's electronic focus control feels a little loose and touchy—even with the aid of frame magnification and the OM-1 II's fantastic viewfinder, I had to manipulate it deliberately to nail critical focus with this one. The original lens is also focus-by-wire, but its clutch has more drag and provides a far more enjoyable, manageable manual focus experience.

(Credit: Jim Fisher)

Autofocus, on the other hand, is rock solid. The 17mm F1.8 II snaps to the point of focus in an instant without any noticeable hesitation or delay. There is a visible bloom in the angle of view when shifting focus from a close to a far-off subject, an effect called focus breathing. This isn't a concern at all for photography, but if you are using the lens for video, you'll want to be aware that the lens is less than ideal for scenes that rack focus from one subject to another as a narrative device.

OM's specs list the lens as having a 9.8-inch minimum focus distance, with its metric equivalent (0.25m) actually engraved on the lens barrel. I was a little surprised to discover that my review sample focused much closer, in the neighborhood of 6 to 7 inches from the sensor plane, which let me get tighter shots of flowers and other small objects. So while the specs may have you believe that the best magnification you'll get is 1:12.5, my close focus tests with a ruler show that the actual figure is closer to 1:7.7, not close to life-size macro, but better for close-up imaging.

(Credit: Jim Fisher)

I asked OM about the discrepancy and a representative told me the listed 0.25m distance is where the lens delivers its best performance, and focusing closer will blur the edges of a scene when photographing a flat field. I noted the blurred edges for sure, but they are of no concern when photographing a subject against a blurred-out background, which is the more typical use case for focusing close with a moderately wide, bright aperture lens. All and all, the closer-than-advertised focus is a net positive and translates into some additional, unadvertised versatility in use.

(Credit: Jim Fisher)

Image Quality: Excellent Results Aside From False Color

I took the M.Zuiko 17mm into our testing studio to analyze its resolving power using Imatest software. When paired with the 20MP OM-1 Mark II, the lens scores in the very good range at f/1.8-2 (2,300 lines), and crosses over into excellent territory at f/2.8-8 (2,400-2,600 lines). Micro Four Thirds sensors are more diffraction-prone than larger ones, so we start to see a drop in clarity at f/11 (a very good 2,350 lines), which becomes more precipitous at f/16 (1,900 lines) and f/22 (1,400 lines). One note: I see a little edge softness at f/1.8-2. You'll get the clearest edge-to-edge results from f/2.8-8, so make sure to stop the aperture down a little bit when taking landscape photos or capturing other scenes where corner-to-corner sharpness is what you're after.

(Credit: Jim Fisher)

You may still find reason to use the narrowest f-stops, however. The same optical diffraction that reduces resolution by scattering light particles as they pass through the lens's stopped-down 9-blade aperture causes small points of light to render as 14-point starbursts from f/11-22. It's a nice effect that can add some sparkle to scenes with the sun either in frame or glinting off objects like bright metal or the surface of water.

(Credit: Jim Fisher)

The optics exhibit some barrel distortion if you look at a Raw image without any correction applied, but you'll need to make an effort to do so. OM smartly embeds a correction profile right into the Raw images for this lens so scenes are rendered with correct geometry, just like with JPGs. Your Raw conversion software may allow you to disable the profile, and you may want to for some scenes as the lens shows a slightly wider angle of view with the profile disabled, but for most scenes, I'd recommend leaving the profile turned on.

(Credit: Jim Fisher)

I'm pretty happy with how well the lens suppresses flare. I took several images with the sun or another bright light pointed right into the lens and only noticed a small bit of false blue color in the scene. This is one of those lenses where the hood's main job is protecting the front glass from damage, so some extra flare resistance is a nice bonus.

Micro Four Thirds cameras don't blur backgrounds as easily as full-frame chips, but you can still coax a good deal of bokeh out of the 17mm F1.8 II, as its field of focus is relatively shallow at maximum aperture. The look of the backgrounds is a slightly mixed bag, however. I like that defocused highlights render with softened (but overly bright) edges, without any sign of false onion skin texture. The bright edges can introduce a frenetic look to bokeh for certain scenes, especially those with brightly lit foliage in the background.

(Credit: Jim Fisher)

There is quite a bit of false color apparent in the blur. I see heavy purple and green fringing along the edges of subjects that are just off the plane of focus in certain scenes, including around blurred tree branches and bright specular highlights. You can see the effect at its worst in the upper left portion of the frame in the following image. These are the typical problem areas for this type of false color, called longitudinal chromatic aberration (LoCA), which is all but impossible to remove using editing tools.

(Credit: Jim Fisher)

The LoCA effect lessens if you set the f-stop to a narrower aperture (f/2.8-5.6), the trade-off being that the lens doesn't blur backgrounds as much at those settings. LoCA is a situational issue meaning you won't see the effect in every picture, but if you are sensitive to false color, it's a mark against this prime. Both similarly priced alternatives, the Lumix G 15mm F1.7 and the Sigma 16mm F1.4 Contemporary, also show LoCA in these scenarios, leaving you to spend more for the larger, heavier M.Zuiko 17mm F1.2 Pro if you want a Micro Four Thirds prime with extra bright optics and very little false color.

(Credit: Jim Fisher)

Verdict: Small, Sealed, and Sharp

The original M.Zuiko 17mm F1.8 has been around long enough to be a known quantity among photographers using the Micro Four Thirds camera system. The prime was a standout at its time of release and won us over in review with its slim form and manual focus clutch. The 17mm F1.8 II matches its predecessor in picture quality, drops the focus clutch, adds weather sealing, and maintains a featherweight, carry-friendly design, These features make it a better match for OM's line of svelte, outdoor-friendly mirrorless cameras than bigger glass like the Sigma 16mm F1.4 DC DN Contemporary. We certainly don't love the LoCA, but it's the only notable drawback, and not nearly enough of a problem to keep the lens from earning the same Editors' Choice endorsement as the original.