Panasonic Leica DG Summilux 15mm f/1.7 ASPH. lens
(non–)review and post–optics

Whenever I buy a new lens, I first run some basic tests. Properly done, lens testing is a weighty undertaking: you need to examine a number of performance factors at different distances and for a handful of lens copies to account for sample variations (and if you buy a zoom lens, good luck). I do not have access to multiple lens copies, and I am usually not interested in performance at close distances. Thus, the purpose of my tests is not to pronounce the ultimate verdict; instead, it is to determine whether my copy of a lens is an overall decent performer, how well it performs wide–open, what aperture setting delivers best image quality, as well as what aperture I choose for maximum depth of field*. I further look at a lot of real–life images to see if any peculiarities draw my attention. Once I am satisfied that a lens is a keeper and know what I need to know, I move on.

Panasonic Leica DG Summilux 15mm f/1.7 ASPH. lens (image courtesy of Panasonic)

I should first mention that the Summilux is a sexy lens. Design is clean and consistent with Leica's established and easily recognised aesthetic. The lens is made of metal and, while not heavy, has a nice heft to it. Operation of the aperture and focus ring is smooth as butter, and it balances very well on the Panasonic GX8 (although it is a relatively large camera in the M4/3 camp, I envision the lens would be right at home on any Panasonic or Olympus body). Overall, the Summilux exudes an air of a high quality product and reminds me of some of the better–built lenses of film era.

Looking at test files in Adobe Lightroom and prints from converted files, I was quite impressed. Essentially, there is no light fall-off or distortion, and only a slight touch of chromatic aberration is noticeable every now and then. Centre sharpness is already quite good at f/1.7, improves slightly and peaks at f/5.6, and diffraction starts taking its toll from f/8 onwards. Corner sharpness largely follows the same pattern and, as expected, is somewhat worse than in the centre. Flare can be a big problem at certain angles to light sources, but it does not occur often and is easily solved by moving the camera a bit. All things considered, not too bad at all if you ask me.

Pixel–peeping various real–life images, however, I started noticing minor artefacts and sometimes inconsistent sharpness at micro–level. For lack of a better way to explain it, there were random areas of worse, or strange, sharpness where you would not expect it. It is fairly subtle and does not happen all the time, but, if you look at enough images, it is clearly there.

I then found the following hidden notice in Lightroom: "This raw file contains a built–in lens profile for correcting distortion and chromatic aberration. The profile has already been applied automatically to this image." Applying the profile cannot be turned off in Lightroom. As I suspected, there is no free lunch after all: uncorrected files in DxO Optics Pro showed a very different picture.

Lumix G Leica DG Summilux 15mm f/1.7 ASPH. lens: distortion prior and after correction

First, the lens produces massive barrel distortion: the image above shows the corrected version; roll your mouse over it to see the uncorrected original. Note that correction of distortion involves quite a bit of cropping. Second, the lens produces a notable amount of chromatic aberration as shown below. Although I did not check it, I suspect the same goes for light fall–off.

Lumix G Leica DG Summilux 15mm f/1.7 ASPH. lens: uncorrected chromatic aberration

Considering the notice in Lightroom and that distortion is of a simple barrel kind (i.e., relatively easy to correct in software), I can only deduce that post–processing software corrections were a part of the lens design**. The benefit is obvious: correcting these aberrations optically would have required adding extra glass element(s), which would have made the lens bigger and more expensive. The downside, however, is not exactly pleasant: artefacts and sharpness degradation caused by correction of the aberrations in post–processing.

Which brings us to the main point of this review: we are entering the era of post–optics***. In other words, it is now half–optics, half–software, and optics are increasingly taking a back seat****. Software will be getting better and better, allowing increasingly more room to relax optical design. From this perspective, traditional lens tests have become inconclusive: while you can dissect what optics deliver of and by themselves, the conclusions will largely depend on the philosophical notion of whether you accept after–the–fact software corrections as an inseparable part of your lens.

Where do I stand? In all honesty, I feel conflicted.

When I look at photographs printed at 300dpi to A3+ size from files produced by the Lumix GX8 and the Summilux, they look marvellous. Are correction artefacts visible in prints? They may be, if you know what and where to look for and examine prints very closely; non–photographers would not notice them, though, so for all intents and purposes the prints are flawless. So if you are interested in photography as an art form and photographic content, who cares how technical perfection is attained? As they say, whatever works.

With this being said, however, I do appreciate and value fine optical design in the pure, traditional sense. I do care for lenses that deliver outstanding results without relying on software corrections. Somehow, deep down inside—and I know this may be quite irrational—what the Summilux offers seems, well, dishonest. It makes me want to take out my Hasselblad 503CW, mount one of the superb Zeiss lenses on it, and shoot some film.

So is the Summilux a good lens? Hmm... the answer will depend on which day of the week you ask me on.

Update

A while ago I thought of comparing the lens in question with... the one on the Ricoh GR camera. This juxtaposition is, of course, completely silly: the lenses are of different equivalent focal lengths and used on sensors of different sizes, aspect ratios, and pixel counts. And yet, it made sense to me as it could answer one very practical question: equivalent focal lengths are actually fairly close (30mm vs. 28mm), so which do I pick when I can only take one and want to get the best image quality?

I made some tests and, long story short, here is what I observe. In the centre, both lenses are plentifully sharp; the combination of the Summilux and the Panasonic GX8 shows more detail due to the higher resolution of the sensor and higher magnification of the lens. The difference is far from dramatic, though—both look great. In the corners, however, the picture is quite a bit different: the lens of the GR delivers notably sharper results. This is no mean feat, considering that the GR is at a considerable disadvantage in this comparison (focal length is shorter and magnification is thus smaller; resolution of the sensor is also not as high).

All things considered, it is a toss–up, more or less, even though overall I prefer the files from the GR (they offer more editing leeway, pixel–level acuity is better, base ISO noise is less pronounced, and high ISO performance is superior). Again, though, A3+ prints from both camera–and–lens combinations look remarkable.

Unexpectedly, the result of this exercise turned out to be different from the original intention. Instead of helping to choose one camera–and–lens combination over the other*****, it has served to put things into perspective.

If anything, it has offered a fresh look at the Ricoh GR—the camera just does not stop amazing me. It is four years old, the rubber grip has started to come off, and the LCD screen cover is badly scratched; I had to repair the lens once, sent the camera in to Ricoh to clean dust off the sensor twice, and bought a new ring cap to replace the lost one; it is also certainly showing its age: autofocus is twentieth-century slow and the camera is decidedly disconnected. Yet, image quality remains highly competitive, and camera usability (controls and user interface) is still to be beaten in many respects. I just cannot let go of the camera despite its deteriorating condition and lack of modern features.

And now back to the subject of this review. The Summilux is a decent lens (again, only if you accept software correction of aberrations as part of the lens design). It will not disappoint you under most circumstances. You will be able to make beautiful prints from files shot with it. All this being said, optical performance of a lens does not exist in a vacuum, and, when considered in the context of other lenses' capabilities, I cannot say the Summilux is an admirable performer. Which is my final verdict: it is a good, but far from great, optic.

*I am essentially a minimalist who only needs three aperture settings: wide open for maximum light gathering and/or shallow depth of field, the aperture where image quality is best, and the setting where depth of field is deepest while diffraction is still not too bad. I would be happy to remove the rest of apertures from my lenses. Imagine the lens pictured above with just three settings: f/1.7, f/5.6 and f/11. Beautiful!

**This is not exactly new: I observed the same phenomenon a few years back when testing the Sony RX–100 camera. What I did not expect, however, was that this would spread to high–end lenses and flagship camera models.

***In this context the prefix post means that something belongs to a time in which it has become less important or relevant, as in post–truth.

****Witness the same with the iPhone: with computational photography now a fact of life, we no longer need fast lenses, or round aperture blades, to get beautiful bokeh (we still need larger apertures to gather more light, but I wonder how long this will be necessary).

*****Given that there is no clear winner in terms of image quality, each serves different purposes. Ricoh GR is so small and light it can be carried at all times while delivering stunning image quality; it is always with me on business trips and a perfect companion to my LF rig on dedicated photographic expeditions. The GX8, on the other hand, has a beautiful electronic viewfinder, much faster autofocus, touchscreen, wi–fi, 4K video—and, of course, it can take other lenses (unlike Ricoh GR's lens, I am not married to the Summilux).