Olympus 12-40mm f/2.8 Lens Review

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What is It?

The Olympus 12-40mm f/2.8 was the first of its Pro lineup of lenses, eventually going to be a set of four (7-14mm f/2.8, 12-40mm f/2.8, 40-150mm f/2.8, 300mm f/4). As such, it’s a high performance lens that’s been built at a high level of quality, as well.

Olympus uses their “splash proof" label for the 12-40mm, indicating resistance to dust, water, and cold. The lens is a bit heavier than the similar Panasonic 12-35mm f/2.8, touching the scale 62 grams heavier at 382g (that’s 13.5 ounces in US-speak).

The 62mm front element sits relatively vulnerable at the front of the lens, though Olympus supplies a reversible LH-86 petal-type hood that you can use to give some protection. As you zoom, the lens extends in length by a considerable amount, so don’t get deceived by the 3.3” (84mm) collapsed size; the lens will easily hit 5” with hood when zoomed. Focus does not rotate or move the front element.

Zoom markings are shown for 12, 14, 18, 25, 35, and 40mm. If you pull back on the focus ring you put the lens into manual focus mode and reveal a focus scale. The focus scale has very few markings (1’, 2’, 5’, and .2m, .5m, and 1m, plus infinity). Close focus is a respectable 8” (0.2m), and the lens can produce a 1:3.3 magnification ratio at 40mm, almost putting it into the macro lens range.

The lens has one L.Fn button located about where you would usually have your thumb if you’re holding your left hand under the lens. I outline the L.Fn functions in my 40-150mm review. Panasonic camera owners should be aware that the 12-40mm f/2.8 does nothave image stabilization. This might be a deal breaker for some Panasonic camera users (Olympus uses sensor-based stabilization).

Price is US$1000, and the lens is manufactured in China and only available in black.

How’s it Handle?

Overall, the action of the focus and zoom rings are quite excellent. They’re exceptionally smooth, though a little on the loose side compared to some lenses. Unfortunately, it’s difficult to distinguish between the two rings via touch, even though Olympus uses a different engraved texture on each ring. Part of that is that fact that they sit close together, part that they’re exactly the same diameter, and part because the material used is a little slick, which masks the change in texture.

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As I noted, the L.Fn button is well located. Likewise, the hood lock buttons are quite easy to find and operate. Even the front lens cap, which uses the pinch-type release, is nicely done and easy to use by touch. Thank goodness, as Olympus small lens caps on their less specified lenses are a real pain to use with gloves on. Not so anything about the 12-40mm. Bravo.

The focus ring clutch system invariably catches some by surprise. They go to change focus method and find that they’re locked into manual focus. Well of course they are, they’ve moved the focus ring back to the manual focus only position. But this can happen as you move the camera in and out of cases, too, so it can be disconcerting if you’re not prepared for it. And yes, I’ve gotten emails from photographers in the field asking how to reset their OM-D so that it would autofocus again. One was a pro. It probably would be helpful if Olympus figured out some way to put a “check lens focus ring” indicator up on the display when the autofocus system gets grayed out that.

The lens balances very nicely on the front of an E-M1, a bit less so on the E-M10, and it’s frightening large on the smallest Panasonic bodies (e.g. GF6, GM1, GM5). The 12-40mm on one of the Olympus OM-Ds is bit like a mini-DSLR experience. My Nikkor 24-70mm f/2.8 is just so large and unloved these days I finally sold it and went back to small primes in the midrange for my FX DSLRs. Olympus has scaled their lenses very nicely with their m4/3 bodies, and that’s one of the things that makes m4/3 use so comfortable.


How's it Perform?

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As with most m4/3 lenses these days, the assumption is that you're going to be shooting JPEGs and using in-camera correction, or using a raw convertor that has lens corrections. So "performance" is getting a little tougher to define these days. Let's start with the "corrected" parameters of the lens:

Linear distortion: Without correction, the lens has a great deal of troublesome linear distortion. At 12mm, it measures over 8% barrel distortion and that doesn't get down to reasonable levels until somewhere about 22mm. By the time you get to the 40mm telephoto end of the lens, things have reversed into about 1% pin cushion distortion. Short answer: if straight lines are at all important to you, you'll absolutely want to correct the output of this lens at all focal lengths except maybe 25-30mm, and probably even there, too.

Of course the camera's built-in corrections take care of much of this, though with a bit of strangeness. At 12mm corrected JPEGs have about a half percent barrel distortion. The oddity is that the camera takes the modest amount of pin cushion distortion at marked 25mm focal length and changes it into a modest amount of barrel distortion! This tells me that the table the camera is using is more a smoothed curve than a very precise set of values for each and every focal length.

Vignetting: Probably the worst of the traits of this lens. Even corrected the lens has high amounts of vignetting in the corners at 12mm (over one stop wide open, two-thirds of a stop even at f/8). Longer focal lengths do better, but I wouldn't call this good corner performance. The good news is that the area of highly vignetted results is very much pushed out into the corners, and it shows a circular pattern. The high overall vignetting levels seem to indicate to me that the image circle of this lens is barely covering the m4/3 frame.

Chromatic Aberration: One of the better aspects of this lens. Even uncorrected the chromatic aberration is well under control, with 40mm f/2.8 being the worst case at just over one pixel's width, and almost every other focal length and aperture being significantly under that. In camera corrections don't take care of all the CA, but they reduce it enough so that you can probably ignore it.

Sharpness: The reason I write about sharpness last in many of these lens reviews now is that correcting the other performance attributes (in camera or in a raw converter) can have a real impact on how the edges resolve. Fortunately, there's good news here. First, this is about the best m4/3 lens I've tested to date in its center performance, and pretty much across the board in both focal length and aperture. 40mm is the weakest in center performance, but it's still very good. At f/2.8 and f/4 I'd tend to say that the 12-24mm performance is superb in the center.Surprisingly, both the converted and unconverted corner performance notches near identical results.

At 12mm there's significant falloff of sharpness from center to edges, but the corners are still better than I'd expect, and I'd rate them very good, even wide open. At 40mm, the corners are still fairly close in resolution to the center, believe it or not. I wasn't expecting these results given the heavy compensations that are necessary to correct the linear distortion.

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Off center performance is good enough that I’m not at all reluctant to put subjects well off center. Yes, this is the full frame I took.


On the other hand, this lens seems optimized for f/2.8 and f/4. Obviously diffraction begins to have an impact overall as you stop way down, but at 12mm, for example, each bit you stop down you lose a little bit of micro contrast. At the opposite end (40mm), that’s true from f/5.6 onward. At the focal lengths in between, the aperture at which you begin to get drops in contrast varies between those f/2.8 and f/5.6.

I wouldn't be afraid to use this lens at any focal length from f/2.8 to f/8, though technically f/4 is probably a slightly "best” aperture overall, and I mean slightly. That, too, is a bit unusual for a fast lens. One other thing that I found unusual: there's very little field curvature at 12mm (or anywhere in the lens, for that matter). I didn't really find myself having to adjust for field curvature or focus shift, which was a bit unexpected.

Bokeh: There's enough spherical aberration that out of focus highlights get the "corona" effect, where the edge of an even circle of light is a bit different in brightness than the centers. Moreover, it appears that the aperture blades in my sample have just a tiny bit of a joint point in them, as I can see that the circle has two distinct "points" on it as I stop down. Thus, the bokeh is nothing to get excited about. It's mostly well behaved, but it's not the dreamy, creamy type many crave.

Overall: You'll be correcting the output of this lens either by shooting JPEGs and letting the camera do it, or you're going to want to use a converter that has a lens conversion ability for this lens. In those cases, you'll get very good results, slightly better wide open than the 12-35mm f/2.8 PanasonicI reviewed earlier. If you don't correct for the lens, you're going to have a lot of linear distortion and vignetting that will rise to high visibility.


Final Words

Panasonic 12-35mm or Olympus 12-40mm? That’s actually a tougher call than it might seem. The Panasonic seems a little more “balanced” between it’s wide and telephoto ends in terms of sharpness. The Olympus beats it at 12mm and f/2.8 but loses to it at 35mm f/4. The Panasonic has more chromatic aberration, though, though their lens corrections do a better job in a number of areas. You can’t really fault either of the two lenses, so the choice really falls to two things.

First, stabilization. If you’re shooting on a Panasonic body, the Panasonic lens probably gets the nod simply because it has OIS and the Olympus does not.

Second, price. If you’re shooting on an Olympus body, the Olympus lens at MSRP is a bit less expensive, so becomes sort of a no-brainer.

In other words, there’s little that I’d use to distinguish between the two lenses. We could quibble. If you’re mostly shooting at the wide end, the Olympus is probably the better choice, but if you’re mostly shooting at the telephoto end, the Panasonic probably is the lens of choice, despite it’s 5mm shorter length. But I don’t think most people think of a workhorse mid-range zoom that way: they want it to be useful across the board. Both these lenses are, just with different nuances as you move through the focal and aperture ranges.

Recommended (in Thom’s m4/3 bag)

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