Plugged In: Zoom in on quality when buying lenses

By Joe Kashi, for the Redoubt Reporter

An excellent lens makes good images even with a mediocre camera body while a bad lens mounted on an excellent camera merely highlights its optical mediocrity.

While camera bodies and their digital sensors continue to improve noticeably each year, lens lineups change very slowly, with many years between updated designs. Over time, it’s likely that most photographers using interchangeable-lens digital SLR and mirrorless system cameras will spend more buying additional lenses for their camera systems than they’ll spend for the cameras mounting their lenses.

That makes sense when you consider that a good lens is an investment that’s usable for decades, while constant improvement of digital sensors means that you’ll probably upgrade your camera body every few years. However, your initial choice of a camera system is a very important long-term decision because most lenses are readily usable only with the camera brands for which they’re designed. Once you’ve started buying some good (read: usually not cheap) lenses, you’re basically locked into that camera system unless you’re willing to completely change your camera system, at a significant financial cost.

Although dSLR cameras from Nikon and Canon continue to dominate interchangeable-lens cameras, the only camera market that’s still growing, mirrorless compact system cameras are slowly gaining traction and market share around the world. As with the original Leica, most people are willing to give up a bit of image quality in return for greatly increased portability. Nine prominent camera makers are marketing compact-system cameras, but nearly all are hampered by the limited number of good-quality lenses available for those cameras.

I decided to buy Micro Four-Thirds (M 4/3) cameras personally, because there’s a far wider variety of lenses that mount directly on Micro Four-Thirds cameras, over 30 at last count from Olympus and Panasonic, with more on the way from third-party lens makers like Sigma, Tamron and Schneider. There was a wide variety of good M 4/3 lenses and I expected that the M 4/3 camera bodies would catch up quickly, as they did. Any brand M 4/3 lens can be used on either Olympus or Panasonic M 4/3 cameras, though they’ll be stabilized only on Olympus bodies.

Other compact-system cameras, like the Sony’s NEX cameras and Fujifilm’s X series, include excellent camera bodies but only a few lenses, at best. There’s arguably only one truly good zoom and one excellent prime lens for the Sony NEX series, while Fujifilm users can choose between a nice, 18- to 55-mm zoom and four sharp prime lenses, 14-mm and 18-mm wide-angle lenses, a 35-mm normal lens, and a short 60-mm telephoto. That’s not much of a system and confirmed my decision to buy M 4/3. That’s an admittedly roundabout way of introducing this week’s topic, a comparative look at the optical quality of a wide range of lenses for M 4/3 cameras.

When evaluating a possible lens acquisition, there are several factors to consider. Zoom lenses are usually not as sharp as single-magnification, “prime” lenses and certainly not as “bright.” How sharp is the lens, not only in the center, but at the edges? There’s often, but not always, a very noticeable degradation of image quality at the edges, particularly when the lens is used at its larger openings. Does the lens improve enough as you select smaller apertures to be generally useful in many different lighting conditions? The best lenses show good edge-to-edge sharpness by f/4 to f/5.6, particularly when you’ve properly exposed the image. Bad exposure reduces sharpness as well as many other image qualities.

Does the lens have good contrast or does bright background light tend to degrade the image? What happens when you’re shooting into a bright light source like the sun? The best lenses usually show only minimal flare and degradation when shooting against a bright background or directly into a bright light source while other lenses are virtually unusable.

Every lens has a limited range of aperture settings that produce the best overall image quality. These are not entirely predictable and vary from lens to lens, so you’ll need to make your own tests. Generally, we’ll find better edge-to-edge image quality when the lens is closed down one to two aperture stops, i.e., setting a lens with an f/2.8 maximum aperture to f/5.6 or so. Going too far, though, will result in unavoidably reduced image quality because of a physical property known as diffraction. As a result, even a really good M 4/3 lens used at, say, f/11 or f/16 usually doesn’t look its best.

  • Comparing M 4/3 lenses: Let’s take a look at the strengths and weaknesses of some of the better M 4/3 lenses. Remember to multiply any M 4/3 focal by 2x in order to get the 35-mm equivalence. All of the lenses listed below are very good to excellent except as specifically noted. I would use any and all of them for critical personal work.
  • Using a 16-megapixel Olympus OM-D, I personally tested every lens mentioned here, usually by taking photos of very fine branches and twigs against a cloudy but very bright sky and comparing the results from each lens against the others. Although inherently somewhat subjective, these real-world comparisons test not only a lens’s inherent sharpness, but also its internal contrast and resistance to flare. I loaded all images into Adobe Lightroom 4 and made normal post-processing corrections for sharpness, “clarity” and red/green chromatic aberration.
  • Olympus 9- to 18-mm ED zoom: This superwide-angle zoom is basically intended for Olympus’ large Four-Thirds professional dSLR cameras, but works great on M 4/3 cameras with an Olympus MMF-2 adapter. I found this older-style 9- to 18-mm zoom to be surprisingly sharp at all magnifications when used at its optimum apertures in the f/6.3 to f/7.1 range. Flare was not a serious problem, even when shooting into the setting sun. Extreme wide-angle lenses like this are difficult to fully correct, but I would not hesitate to use this lens for professional photography if you’re careful to limit your lens aperture to the f/5.6 to f/8 range and expose carefully. I found its edge-to-edge sharpness comparable to Olympus’ very expensive 12-mm f/2 wide-angle lens, at a lower price and with more versatility. (About $375 used.)
  • Panasonic 14-mm f/2.5 wide-angle lens: This is a very small, light (55g) lens that is quite sharp everywhere but the extreme corners (about $300 new). It’s a good substitute of Olympus’ pricy 12-mm lens.
  • Sigma 19-mm f/2.8: Comparable to the classic 35-mm wide-angle lens from film days, Sigma’s 19-mm lens is very sharp in the center by f/5.6, with edges sharpening nicely by f/7.1 to f/8. I tested two different samples, with the second lens doing better at the edges by f/5.6. At current prices, this is one of the least-expensive M 4/3 lenses and an excellent buy, particularly if you buy Sigma’s two-lens kit for M 4/3 cameras that includes both their 19-mm and 30-mm DN lenses ($200 for two lenses plus minimal shipping from BH Photo.)
  • Sigma 30-mm f/2.8: Very good to excellent contrast, detail and center and edge resolution by f/5.6. It’s an unbelievable bargain when bought with Sigma’s $200 two-lens kit (see above).
  • Panasonic 20-mm f/1.7: This is the classic, near wide-angle lens for M 4/3 cameras and is virtually without any serious shortcoming. It’s small, light, and razor sharp at all normal apertures. Cheap, though, it’s not, at $350 or so.
  • Panasonic-Leica 25-mm f/1.4: This is another excellent M 4/3 lens that’s exceedingly sharp and crisp edge to edge by f/4. It does have one noticeable problem — there’s a lot of flare when you’re shooting directly into a bright light source, like the sun, more than any other M 4/3 lens that I’ve used. Despite that, it’s the lens that I leave on my OM-D.  With its recent average retail price of $499, it’s at least vaguely affordable without too much anguish.
  • Olympus 35-mm f/3.5 (about $200 new) and 50-mm f/2 (about $450 new) macro lenses: Both of these extremely sharp macro lenses were originally intended for Olympus’ professional dSLR cameras. Though bulky relative to compact M 4/3 cameras, they’re excellent general-purpose prime lenses in addition to their macro capabilities. You’ll need an Olympus MMF-2 adapter to use these lenses in fully automatic mode. The 50-mm f/2 is so good that it’s used as the supersharp reference lens when testing new M 4/3 cameras.
  • Olympus 45-mm f/1.8: A classic portrait and short telephoto lens. I cannot find any significant fault with this lens, nor can most professional reviewers. It’s quite small, light and, at $400 list price, very reasonably priced for its excellent optical quality. The only possible drawback is the good-quality plastic, not metal, body. I did not find this a concern personally.
  • Olympus 75-mm f/1.8: This lens is definitely expensive ($900) and worth every penny if you’re serious about supersharp medium telephoto shots. Professional lens reviewers claim that it is one of the sharpest and best lenses that they’ve ever tested. It’s certainly the sharpest lens that I’ve ever used, including Leica lenses, and has excellent contrast and good resistance to flare from bright lights. It has no known optical weaknesses and, with a solid metal body, construction quality is excellent.

Next week, we’ll finish up with telephoto and zoom lenses for Micro Four-Thirds cameras.

Local attorney Joe Kashi received his bachelor’s and master’s degrees from MIT and his law degree from Georgetown University. He has published many articles about computer technology, law practice and digital photography in national media since 1990. Many of his technology and photography articles can be accessed through his website, http://www.kashilaw.com.

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