Comparative lens review: The Olympus M. Zuiko Digital 17/1.8

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Advance note: Images in this review were shot with an Olympus OM-D and the ZD 17/1.8 unless marked otherwise. Please go by the commentary rather than the reduced crops; I am looking at uncompressed RAW files on a calibrated monitor, not a websize JPEG. The review was completed with a final pre-production prototype lens. I’m told that image quality and build are representative of the finished product.

_Z260004 copy With (once again) poorly designed and optional lens hood. At this price…shame on you, Olympus.

One of the first lenses released for the fledgling Micro Four Thirds system was the 17/2.8 – equivalent to 34mm in full-frame talk, and the staple walk-around lens for most photographers. I’ve personally never been a fan of this focal length – it simply doesn’t fit with the way I see – so I tried it once on the first E-P1, and never paid it much attention since. That lens was a simple 6/4 design with a single aspherical element at the rear, and notorious for managing to pack many undesirable qualities into a single lens at once – it was slow to focus, suffered from serious lateral chromatic aberration at the edges at pretty much all apertures, and was extremely noisy while hunting to boot.

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Tuna.

Its sole redeeming graces were that it was sharp in the center of the frame, and very small. Most photographers ditched that lens for the Panasonic 20/1.7, which was a little longer, not much bigger, but over a stop faster and optically comparable. That lens made its way into my bag while I was shooting with the E-PM1 Pen Mini, turning the camera into a small and pocketable companion.

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Silhouette of a man

Olympus has been on a bit of a roll lately with its Micro Four Thirds lenses – first the 12/2, followed by the 45/1.8, then the 75/1.8 and 60/2.8 – the latter two of which are amongst the best lenses I’ve used for any system, period; the new M.Zuiko Digital 17mm f1.8 (hereafter known as the 17/1.8) is the latest to follow in this vein.

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What lurks beneath

The lens’ construction is closer to the 75 and 12mm lenses than the 45 and 60, which is to say it follows the High Grade requirements of being all-metal in construction (champagne-colored anodized aluminum) and having the ZERO optical coating. It has the same pleasant tactility and solidity as the 75 and 12mm lenses; there’s no plastic to be seen anywhere here. Unfortunately the lens is not weather sealed and has no visible gaskets, and once again, has an optional (and expensive) lens hood that makes it very difficult to remove the lens cap. Like the 12/2, the full-time manual focus ring override clutch activated by pulling the focusing ring backwards towards the camera. In this position, the ring exposes the distance scale which works in conjunction with the depth of field scale engraved on the static outer flange, and has fixed end stops at minimum focus distance and infinity. Unlike the 12/2, the possible distances are no longer fixed to several discrete ranges – pulling back on the ring and turning it slowly through its range of travel, you can see via the LCD image that the focus distance changes continuously. If there are discrete steps, they’re very small ones. This is great news – whilst the idea was a good one for reactive documentary photography, its implementation on the 12mm made it fairly useless in practice.

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Hop to rainbow row

Needless to say, autofocus speed is on par with all of the current generation of Olympus lenses – very, very fast indeed. It’s much faster than the 17/2.8 and Panasonic 20/1.7 – about the same as the 12/2, and slightly faster than the 45/1.8 (which is to be expected because that lens has a longer focus travel as required by its focal length). I did experience one or two issues with precision at longer distances wide open though – admittedly an unlikely usage scenario – the lens tended to lock at about 6-10m distance instead of infinity; as a consequence, images were borderline sharp but nowhere near what the lens can produce if focused properly. The 17/1.8 focuses down to a minimum of 25cm, which in practice means covering a 15x20cm object or thereabouts. It’s slightly less than the 20cm minimum of the 17/2.8, but curiously the real focal length of the 17/1.8 seems to be a bit longer, which lands up evening things out in the end. Close up performance wide open is not its strength; there’s a distinct loss of microcontrast that robs resolving power, that only starts to come back at f2.8 and smaller – this isn’t entirely surprising as the lens lacks any floating elements. In this area, I’d say it’s on par with the 20/1.7, and slightly worse than the 17/2.8.


Optical formulae. 17/1.8 at left, 17/2.8 at right.

The 17/1.8 is a much more complex lens than the 17/2.8 that preceded it. Firstly, focusing takes place entirely within the lens, in order to keep things fast and silent; the entire optical assembly no longer moves. It’s a complex 9/6 design that appears to have been done entirely by computer; I don’t recognize the optical formula at all. Olympus have spared no expense here – two aspherical elements, one HR element, and one DSA (double super aspherical) element go into the mix. Both front and back surfaces are flat, which presumably has a positive effect on flare; I certainly didn’t see any during my test images, which included several deliberately backlit shots and point sources within the frame. No doubt the ZERO coating helps, too.


MTF charts. 17/1.8 top, 17/2.8 bottom. Image from Olympus Malaysia

On the basis of the MTF charts alone, both lenses should perform similarly in the center, with excellent overall sharpness and contrast, and middling to good microcontrast. Towards the outer portions of the frame, the 17/2.8 drops in fine resolving power, and loses it in the corners. This is not because the lens isn’t sharp: huge amounts of chromatic aberration mixed in with field curvature rob resolving power. The 17/1.8, on the other hand, maintains its overall resolving power out much further towards the edges – remember this is at f1.8, against the 17/2.8 at f2.8 – with a dropoff only in the extreme corners. The complex wave form of the 60 lp/mm lines suggests that it’s probably due to some very odd field curvature, probably as a result of the complex optical design. The 17/2.8, on the other hand, has a simpler, less corrected, design, with resulting first- and second- order uncorrected field curvature. Geometric distortion is very low, however, and requires almost no correction in Photoshop.

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In a very quiet back alley somewhere, waiting for the person to complete the shot that never arrived.

In practice, what this means for sharpness is that the 17/2.8 was good in the center, but terrible in the corners and lacking punch and transparency. From what I’ve seen, the 17/1.8 markedly improves on this in practical situations; the sweet spot extends much farther out from the centre even wide open at f1.8, and by f4 performance is uniformly excellent across the entire frame – in some ways, reminiscent of the behaviour of the 12/2. Note that this is a lens which performs best if you place the focus point over the intended subject; focus-with-the-center-point-and-recompose is not going to yield optimum results due to the nature of the 17/1.8′s field curvature profile.

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Whole test scene.

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3-way comparison of center resolution. 100% version here. The 20/1.7 has the highest overall scene contrast, but the 17/1.8 wins out in microcontrast and reproduction of fine detail structures – personally, I prefer this as it gives me more latitude for processing before the shadows and highlights block up. The 17/2.8 is in the middle for macro contrast and on par with the 20/1.7 for microcontrast.

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Top right. 100% version here. Note purple fringing on the 20/1.7 shots, even at 5.6. That portion of the building is not overexposed according to the histogram. The two Olympus lenses exhibit notable CA, with the 17/2.8 being the worst offender.

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Top left. 100% version here. The 20/1.7 is oddly free of both CA and purple fringing in this corner; in fact, the performance here doesn’t really match the other corners – chalk it down to sample variation. This is the 17/1.8′s worst corner.

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Bottom right. 100% version here. We’re now seeing CA from all three lenses, with the 17/2.8 once again faring the worst. The 17/1.8 is slightly better than the 20/1.7. Interestingly, not much changes even when you stop down.

What will affect resolution (and perceived acuity) far more is lateral chromatic aberration. The 17/2.8 was notorious for this, and to be honest, the 17/1.8 shows a notable improvement over its predecessor, but CA is still present to f4. Both lenses have visible longitudinal chromatic aberration and spherochromatism that show up as fringes in the bokeh; the new lens is slightly better but still not perfect. This does not affect microcontrast as much as you would expect as the longitudinal CA occurs only in out of focus areas, which are devoid of microcontrast and fine detail structures anyway. In the in-focus areas, microcontrast delivered by the 17/1.8 is already good wide open, improving slightly to peak at f4. The 17/1.8 has about the same global contrast as the 17/2.8 at comparable apertures, but slightly better microcontrast and the ability to render more subtle tonal gradations.

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Whole test scene. Yes, that’s a Lego chess set. A custom one: goons vs. the village people.

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Bokeh, LoCA and spherochromatism, #1. 100% version here. I’d say the 20/1.7 looks best here, but it’s very nearly a tie with the 17/1.8.

Both lenses have surprisingly consistent color rendition despite their vastly different construction and coatings; that is to say, neutral to slightly warm, with decent (but still plausibly natural) saturation. Where they differ is in transmission: (see this article for the difference between T stops and f stops) it’s clear that the coatings used in the new lens endow it with significantly better lower internal reflection properties than the older lens. Despite having more elements and air-glass surfaces, the 17/1.8 meters with a shutter speed that’s about 1/3-1/2 stop faster than the old lens for a given fixed aperture and histogram (luminance) output. This is a useful gain in practical situations; it’s not quite see-in-the-dark territory, but good transmission characteristics combined with its relatively short focal length and the excellent stabilization system on the OM-D mean that its useability envelope is very wide indeed. Vignetting is also fairly negligible too, even wide open.

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Bokeh, LoCA and shperochromatism, #2. 100% version here. No prizes for guessing the 20/1.7 has the best rendition since it also has the longest focal length; this portion is a bit of a lopsided comparison.

The 17/1.8 renders out-of-focus areas with a rounded softness and lack of hard/ bright edges or double images, even against complex background textures. Whist you’re never going to get a large amount of defocus to your backgrounds with a real focal length of 17mm (that’s a property of the focal length) unless you get very close to your subject with a simultaneously distant background, what you do get with the 17/1.8 is very pleasant. I actually think the 17/1.8 delivers close to the right amount of bokeh for most situations at relatively near distance; enough to separate the subject but not so much as to completely abstract out backgrounds.

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Fear of the supervisor

Throughout this review, I’ve talked a lot about its predecessor, the 17/2.8; the other dark horse sitting in the corner is the Panasonic Lumix 20/1.7 G. It was my mainstay lens on the E-PM1 Pen Mini, though I’ve used it less since acquiring the 12/2 and 45/1.8 lenses. Though it has a slightly longer real focal length at 40mm equivalent, in practice the difference is minimal and no more than a step or two backwards or forwards. The 20/1.7 is a popular lens amongst enthusiasts because it was both fast and compact; value for money, too, if purchased with the original GF1 kit. It still retains its popularity today, because the only other fast 35-ish equivalent so far has been the Voigtlander 17.5/0.95, which is not only hideously expensive, bulky and manual focus only – all of which somewhat defeat the point of Micro Four Thirds.

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Caged laundry

What I find curious is that the 20/1.7 images render as though they are a slightly cropped version of the 17/1.8 – this is a good thing, as the optics on the 20/1.7 are excellent. Sharpness/ resolution, microcontrast, color transmission and even quality of bokeh are very similar; however they have completely different optical design philosophies. Where the 17/1.8 makes significant gains over the 20/1.7 is in autofocus speed; it’s simply night and day; not to mention the usefulness of the manual focus clutch.

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Hipster at sunset

For the 35mm (or therabouts) EFOV enthusiast, we now have four choices in the Micro Four Thirds mount – the Olympus 17/1.8 and 2.8; the Panasonic 20/1.7, and the Voigtlander 17.5/0.95. There are also myriad other options you could adapt from other mounts, such as the excellent Zeiss ZM 18/4. I’d consider the adapted options not viable simply because none of them were designed with telecentricity in mind, yielding poor results on M4/3 cameras – severe vignetting, color shifts in the corners and purple fringing are all common problems. The Voigtlander is an intriguing lens and a surprisingly excellent performer at f1.4 (it’s decent at f0.95) that also happens to have a very short minimum focus distance of just 15mm from the sensor, but it’s very much a special-purpose lens: you don’t buy this and shoot it at f2.8. There’s simply no point. And if you need one, I think you’ll already know it.

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Waiting for the bus

That leaves us with the three native AF options. I would not buy the 17/2.8 unless size is a critical priority, or you know that you’re going to be shooting only static objects stopped down; otherwise the slow AF speed will drive you crazy. The Panasonic 20/1.7 is in a similar boat; it’s faster to focus than the 17/2.8 and optically better, but nowhere near as fast as the 17/1.8. The 20/1.7 and 17/1.8 deliver similar resolution in the center, but they render quite differently – the 20/1.7 is punchier but has slightly lower microcontrast; the 17/1.8 has lower macrocontrast but better reproduction of fine detail structures – i.e. better microcontrast. In the corners, the 20/1.7 is the highest-resolving of the three, but shows strong purple fringing on top of CA which is absent from the other lenses. Interestingly, one thing I noticed with all three lenses was that corner performance was not really consistent – i.e. there were some minor tolerance-related astigmatism effects in play. All three lenses still suffer from longitudinal CA and spherochromatism, though. Ultimately, I think your choice will boil down to three things: price (the lens is to be around US$500 when it becomes available in December), whether you prefer the 40mm FOV, or 35mm; and how critical is focusing speed? If you shoot a lot of street or documentary work, then the ability to stop down and scale focus can be an extremely valuable asset. Overall verdict: recommended. MT

Thank you to Olympus Malaysia for supplying the lens review sample.

The Olympus 17/1.8 is available here from B&H

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Images and content copyright Ming Thein | mingthein.com 2012 onwards. All rights reserved

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