Pros & Cons
-
- Compact.
- Built-in hood.
- Impressively sharp.
- Minimal distortion.
- Quick-shift focus system.
- Excellent build quality.
- Fairly even illumination.
-
- Disappointing edge performance at f/4.
- Some chromatic aberration.
- Screw-in lens cap.
- Not weather sealed.
Pentax HD DA 15mm F4 ED AL Limited Specs
| 35mm Equivalent (Telephoto) | N/A mm |
| 35mm Equivalent (Wide) | 22.5 |
| Dimensions | 1.6 by 2.5 inches |
| Lens Mount | Pentax K |
| Stabilization | None |
| Type | Lens |
| Weight | 6.7 |
The Pentax HD DA 15mm F4 ED AL Limited ($549.95) is one of the more impressive lenses in the company's Limited series. Compared with the older Pentax DA 14mm f/2.8 it's downright tiny, but it only sacrifices one f-stop to achieve its size. It's impressively sharp, and shows very little distortion, both feats for a wide-angle lens. The build quality is excellent; highlights include an all-metal lens barrel, a useful depth of field scale, a well-damped manual focus ring, and an integrated lens hood. It's not perfect—edges are a little soft at f/4, I noticed some chromatic aberration, and the screw-in lens cap is a bit of a pain. But it's still a solid lens, and either this HD version or the older SMC version of the DA 15mm should be the go-to wide-angle for Pentax shooters.
Design
This version of the 15mm ($315.00 at Amazon) is an update to the previous SMC DA 15mm F4 ED AL Limited. Cosmetics aside (this model sports a red ring and is available in black or silver), the technical differences are minor. The HD in the lens name refers to the latest HD lens coating, which is designed to minimize the chance of lens flares and ghosting, even more so than the venerable SMC-branded coating that adorned the older lens. The other change is a divisive one: This lens has rounded aperture blades. This mean out-of-focus areas will be a bit smoother. It's possible to get some bokeh by getting close to subjects, but wider angle lenses generally don't give you a very shallow depth of field. The older SMC lens didn't have these rounded blades, which led to points of light (such as streetlights) displaying a starburst pattern around them in shots. Some photographers love this effect, and it's one that you won't get from the HD DA 15mm.
The lens measures 1.6 by 2.5 inches (HD), weighs just 6.7 ounces, and uses 49mm filters. Compare this with the SMC DA 14mm F2.8 ED IF; that lens is just a smidge wider and one stop faster, but is 2.7 by 3.3 inches, weighs 14.8 ounces, and uses 77mm front filters. The integrated hood is a telescoping design that collapses into the lens barrel when not in use. A screw-in lens cap is included; like the lens, it's metal—there's no plastic here.
The focus ring supports Pentax's quick-shift system. Once the camera locks autofocus, you can make a quick adjustment by simply turning it, without having to change settings. If you opt for manual focus, the depth of field scale comes in handy. Just set the lens to a narrow aperture and move the infinity marker over to the corresponding marker on the scale, and you'll be able to capture in-focus shots with very deep focus.
The lens focuses to 7.1 inches (18cm), pretty typical for a prime with this angle of view—when paired with an APS-C camera, it covers the same angle as a 23mm lens on a full-frame system. It doesn't enter macro territory, but you can get pretty close to subjects, capturing a wide swath of background behind them.
Image Quality
I used Imatest to check the sharpness and distortion characteristics of the 15mm when paired with the 24-megapixel K-3($419.00 at Amazon). It shows virtually no barrel distortion worth mentioning (0.8 percent), and exceeds the 1,800 lines per picture height that we use to mark acceptable resolution at every tested aperture.
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That score is computed using a center-weighted testing method; at f/4 the DA 15mm resolves 2,046 lines. At this wide aperture the extreme edges of the frame are a bit soft, scoring less than 1,000 lines, and I did notice some drop-off in real-world shots at f/4 that corresponded to the lab tests. Narrowing the aperture helps to improve things; at f/5.6 the lens manages 2,202 lines, with 1,268 lines at the edges, and at f/8 the center-weighted score improves marginally (2,236 lines), but edges are a much better 1,493 lines.
I did see some chromatic aberration in high-contrast areas, notably where a dark object was against a bright sky. At f/4 they show up quite often, but are pretty easily removed with just a few clicks in Lightroom. They are less evident at narrow apertures, though I did manage to pixel peep some purple fringing in an f/8 shot—but it was minimal. Corners are a little dim at f/4, about 2 stops darker (-2EV) than the center of the frame, but that's a mild drop for a wide angle. The deficit dropst to -1.2EV, and at f/5.6 and beyond the frame is evenly lit from corner to corner. If you shoot in Raw, you can correct it easily with Adobe Lightroom, and if you opt for JPG capture you can enable illumination correction in camera. When that's on you only have to contend with a -1.5EV drop at the corners at f/4.
The HD DA 15mm is intended for use with APS-C SLRs from Pentax. You can mount it on the full-frame K-1 ($1,335.00 at Amazon) and either shoot it as a full-frame lens, or enable an in-camera crop to reduce the captured area to match an APS-C camera. When shooting in full-frame mode you'll see a heavy vignette, with the area of the frame not covered by the 15mm's image circle appearing as black, and some extreme blurring as you move outside the APS-C area. If you pair the lens with the K-1, I recommend setting the coverage area to APS-C (which will still net 15MP images). Since it's not intended for use with a full-frame camera, the lack of coverage doesn't change our evaluation of the 15mm.
Conclusions
If you're a wide-angle shooter, the Pentax HD DA 15mm F4 ED AL Limited is the smallest, lightest lens you can get for your APS-C Pentax SLR system. It's not the widest; there's an older 14mm f/2.8 prime, but it's downright huge in comparison, as well as a 12-24mm f/4 zoom, and Pentax's weather-sealed SMC DA Star 16-50mm F2.8 ED AL (IF) SDM($1,165.97 at Amazon). None of those lenses are as small as the DA 15mm, and none are as affordable. If you're a fan of the starburst effect, it's probably worth your effort to track down a used copy of the SMC version of this lens, but if that's not a concern, the HD DA 15mm will serve you well.
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