By Joe Kashi, for the Redoubt Reporter
Wide-angle lenses present both optical design challenges and unique photographic opportunities.
Photographically, the demagnified images inherent to a very wide-angle field of view and the necessarily close camera-to-subject distances often result in strong and unusual optical effects.
These wide-angle photographic effects are neither good nor bad in themselves. What matters is how you use them, either to make cliched photos or to show a fresh and unexpected point of view of a subject.
As I compared the sharpness of various lenses, I found that affordable wide-angle zoom lenses sometimes did as well or better overall than more expensive prime lenses, at least in the price ranges affordable by mere mortals.
That’s really odd. My guess is that current consumer-grade, wide-angle zoom lenses likely benefit from economies of scale and more modern optical designs.
Wide-angle prime lenses are usually smaller and lighter than zoom lenses with comparable wide-angle magnifications. That seems to be the principal advantage of sub-$1,000 wide-angle prime lenses.
Optically, it’s more difficult to make an affordable wide-angle zoom that’s acceptably sharp from center to corner while avoiding severe optical distortion that makes straight lines curved. Yet wide-angle zoom lenses are often very sharp, particularly at their shortest focal lengths.
However, kit zoom lenses included with APS-C digital SLR cameras generally do quite poorly at the wide end of their magnification range. That’s why this week’s article looks at some affordable optical upgrades.
There’s less reason to upgrade Olympus and Panasonic Micro Four-Thirds (M43) kit lenses. These 14- to 42-mm zoom lenses do quite well in the 14- to 18-mm wide-angle portion of their magnification range.
Used with 35-mm film cameras, lenses with 35-mm and shorter focal lengths were considered to be wide-angle lenses, with very noticeable optical effects starting around the 28-mm focal length. A 24-mm lens was considered to be an “ultrawide angle” on a film camera while 20-mm or 21-mm lenses produced an “extreme wide angle” effect. Few successful lenses shorter than 20 mm were made for film cameras. Optically, it was just too difficult to get sharp corners and edges with 1990s technology.
When considering a lens’ apparent optical effect, we need to take a digital camera’s “crop factor” into account. Nikon, Pentax, Canon and Sony dSLR cameras with an APS-C sensor have a 1.5x to 1.6x crop factor, while M4/3 cameras from Olympus and Panasonic have a 2x crop factor.
As a result, a 24-mm focal length lens used on an APS-C camera or a 17-mm lens on an M43 camera both produce the same mild wide-angle optical effect as a 35-mm lens on a 35-mm film camera. An 18-mm lens on an APS-C camera and a 14-mm lens on M43 cameras produce noticeable wide-angle effects. Sixteen-mm lenses mounted on APS-C dSLR cameras and 12-mm lenses used with M4/3 cameras encroach into “ultra” wide-angle territory. By 12 mm to 14 mm, APS-C lenses definitely show “extreme” wide angle effects, while a 7- to 12-mm lens has the same effect on an M4/3 camera.
At these short focal lengths, only by a few millimeters difference results in a noticeably wider or narrower field of view and quite different optical effects. So, for an APS-C camera, a 12- to 24-mm wide-angle zoom lens produces fields of view and optical effects that range the entire gamut from extreme wide angle to a very mild wide-angle effect.
A curved focus plane often degrades corner sharpness in wide-angle photos, especially when taken at brighter lens apertures like f 2.8. As a result, it’s common for wide-angle lenses to be quite sharp in the center but fade quickly toward the edges and corners. The best way to eliminate, or at least greatly reduce, this problem is to use a smaller aperture, like f 5.6, where the greater depth of field expands the area in front and behind your focus point that’s in sharp focus.
Lest Canon, Sony and Nikon owners feel slighted, I did compare images made with sub-$1,000 wide-angle primes made by these vendors. I felt that while their center sharpness was often excellent, corner and edge sharpness typically wasn’t on par with wide-angle zooms made by the same vendor or less-expensive, third-party lens makers.
That’s not to say that the $2,000 Nikon 24-mm f 1.4 ED lens or the comparably expensive Canon 24-mm f 1.4L lens aren’t sharper over most of their image area. They are, but a $2,000 lens is flying a bit too close to the sun for my taste.
A few affordable prime lenses, mostly for Olympus and Panasonic M4/3 cameras, showed very good sharpness across most of the image.
Panasonic’s 14-mm f 2.5 prime wide-angle lens (about $350) is tiny and very light, a good match for one of the very compact new Olympus or Panasonic M4/3 camera bodies. Although this lens seems controversial, with both good and bad professional reviews, I cannot find any fault with the copy that I own and use on an Olympus E-PL2. I really like its small size and good sharpness, but especially its relatively low cost.
Panasonic’s 20-mm f 1.7 lens (about $350) falls somewhere between a wide angle and a normal magnification lens. It’s worth mentioning, though, because it has a fairly wide field of view, is very sharp, affordable and compact.
Olympus’ 12-mm f 2 ultrawide-angle lens is even sharper — you could metaphorically shave a week-old beard with it. It’s also quite small and very well made with a carefully machined metal body. There are only two drawbacks to this lens — it costs about $800 retail and the Olympus 14- to 42-mm II kit zoom that came essentially free with my E-PL2 camera is nearly as sharp, with a field of view that’s almost as wide. Those are both serious impediments to buying what really is an optical and mechanical gem usable on any M4/3 camera.
Olympus’ 17-mm prime lens is less controversial than the 14-mm Panasonic. Nearly everyone agrees that optically it’s mediocre. The “free” Olympus M. Zuiko II kit zoom is quite a bit sharper at the same magnification, although physically larger.
While we’re on M4/3 cameras, I should mention that there are two excellent extreme wide-angle zoom lenses for these cameras. Olympus’ 9- to 18-mm M. Zuiko zoom (about $675) is really intended for the 9- to 12-mm extreme wide-angle range. It competently covers the entire wide-angle range in a compact and fairly affordable package, although it’s not as sharp in the more common 14- to 18-mm range as Olympus’ M. Zuiko II kit lens.
Panasonic’s 7- to 14-mm zoom lens is something else. No expense is spared to make a zoom lens that’s exceptionally sharp for its extreme wide-angle range. With a selling price in the $1,300 range, it should be sharp. Nothing else goes quite as wide.
Pentax’s 15-mm f 4 and 21-mm f 3.2 Limited edition prime lenses are compact, quite sharp and extremely well-made mechanically. These cost between $550 and $650 but they’re usable only on Pentax APS-C cameras. At the same time, neither Pentax lens is quite as sharp at wide angle settings as the Tamron 17- to 50-mm (non-VC) zoom lens that I previously purchased for about $200 less.
The Tamron’s also faster, with a constant f 2.8 aperture, and reaches out to 50 mm, a mild telephoto effect on Pentax dSLR cameras. The only drawback of that Tamron 17- to 50-mm lens is its greater size and weight.
Tamron sells its 17- to 50-mm lens in two versions. The non-VC (vibration control) version is made in all major camera mounts although it’s best used with Pentax and Sony cameras that build vibration control directly into their camera bodies. It’s an excellent choice for these cameras.
A newer, more expensive model (about $650) that includes vibration control is available for Canon and Nikon cameras. Unfortunately, Tamron’s newer VC version isn’t nearly as sharp as the older non-VC lens and thus isn’t as good an all-around choice. If you’re a Canon or Nikon user who’s willing to use faster shutter speeds and forego vibration reduction, then the older Tamron 17- to 50-mm lens would serve well.
Otherwise, a better third-party choice for Canon and Nikon users is Sigma’s Sigma AF 17- to 50-mm f/2.8 EX DC HSM OS zoom (about $660). Sigma’s lens names are long and arcane but every letter counts here. Be sure they’re all there. This is one of the newest third-party, wide-angle zoom lenses and one of the best third-party lenses along with the non-VC version of the Tamron 17- to 50-mm zoom.
Canon owners have an excellent same-vendor choice in Canon 15- to 85-mm zoom lens ($740). It’s quite sharp from center to edge at all focal lengths and has the added advantage of good telephoto reach at the far end of its range. Were I a Canon owner, this would be my first choice unless I needed an even wider-angle field of view. Nikon’s 16- to 85-mm zoom ($650) is nearly as good in the same price range.
In the more extreme 12- to 24-mm wide-angle range, there are several good choices, all of which are rather bulky mechanically. Tokina’s 12- to 24-mm f4 zoom is an affordable (about $550) option for Nikon, Canon and Sony lens mounts. It’s very sharp for its cost, at least in the 12- to 20-mm extreme wide-angle range. At its maximum 24-mm magnification, though, images are fairly soft.
Nikon’s 12- to 24-mm lens is quite good, with better sharpness from center to corner across the entire zoom range. It’s a substantially more expensive lens, though, retailing around $1,230.
Sadly, Sigma’s 12- to 24-mm offering is not very sharp. I’d avoid it in favor of Tokina’s less expensive, sharper model.
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.