Conclusion - Pros
- Good balance of optical properties for its intended (portrait) role
- Near-silent autofocus thanks to SDM system
- Very good build quality, including weathersealing
Conclusion - Cons
- Relatively slow autofocus
- Inaccurate focusing unless using camera's AF adjust, varying in behavior across camera models
- Very expensive for its class
Let's talk about the positives first; the Pentax smc DA* 55mm F1.4 SDM is undoubtedly a lens capable of producing wonderful images, with a blend of optical characteristics near-perfectly suited to its intended purpose as a portrait lens. Shoot at F1.4 and you'll get flatteringly soft, but still finely detailed images, with characterful, almost painterly backgrounds. Stop down to F2 or thereabouts (arguably the optimum aperture for portraits) and you'll see a touch more sharpness, with slightly smoother, less distracting bokeh. If you want biting definition and more depth of field, shoot at F4 or smaller. All the while that 55mm focal length is offering the angle of view of a classic 85mm lens from the days of film, giving you a slightly longer working distance and more flattering perspective compared to a 50mm prime on APS-C. All in all, the lens is a clear improvement over the smc FA 50mm F1.4, with much superior wide open performance than the older, film-era design (although the gap narrows considerably at smaller apertures).
The build quality is very good too - in fact more than equal to anything else in its class, due to the added bonus of weathersealing. Now you may not make a habit of shooting portraits in the rain, but it's always nice to know the lens should survive a splash or two (just as long as you have it matched to a similarly-sealed body). The SDM focus motor is near-silent, and won't disturb your subjects in the slightest; however it is slower than the screw-drive system of the older 50mm, and while this isn't a big deal if you tend to pre-focus then shoot, you might need to bear it in mind if you use autofocus to track continually and erratically moving subjects - children, for example.
Unfortunately, though, we have serious concerns over two issues with this lens which have to temper our enthusiasm; namely optical alignment and autofocus (which are quite likely related). Over the course of what has become a rather protracted regime of testing, we've looked at three samples of this lens, and each has shown a clear tilt to the focus plane; this was most pronounced in the first sample, but relatively minor in the last (indeed in this sample it was only really detectable in our studio tests). This does more than simply mess up our studio tests - it clearly results in real-world image quality and focusing problems too. In fact we've never before seen a lens so capricious when it comes to focusing - we're used to F1.4 primes being challenging for cameras' AF systems, but the 55mm was most difficult of all. We couldn't get any of the tested samples to focus sufficiently accurately for reliable shooting wide open without resorting to focus adjustment, and the amount required on our K20D body (which focused the FA 50mm F1.4 just fine) was huge, a full +10. The lens worked better on the K-7 we received during the course of this review, but still needed adjustment for best results, although curiously in the opposite direction (-3); but on the K2000 we were left high and dry, unable to achieve accurate focus at all. Based on this experience, it becomes difficult for us to recommend the lens to owners of cameras other than the K20D and K-7, on which AF adjustment isn't available, unless you can test it to your satisfaction first.
The other big problem we simply can't overlook is the distinctly high price. At the time of writing we're looking at $650, which does seem rather steep when compared to the alternatives; $500 for the excellent Sigma 50mm F1.4 EX DG HSM, or a mere $250 for the outgoing Pentax smc FA 50mm F1.4 (by way of comparison, Nikon's new AF-S Nikkor 50mm F1.4G retails for about $470, and Canon's EF 85mm F1.8 USM full frame portrait lens, $380). Now it's fair to say the 55mm F1.4 is much improved over the old FA 50mm F1.4, but the Sigma is a different proposition entirely. It sports both excellent optics and ultrasonic-type focusing, placing it very much in the same league as the 55mm. However it's not weatherproofed, and noticeably short for a 50mm lens (we'd place it closer to 47mm, giving a 70mm equivalent on APS-C), making the 55mm a rather nicer length for portraits.
So providing a final recommendation to this review becomes very difficult. When this lens works properly, it's one of the very best portrait lenses that Pentax users can currently buy. But getting it to work properly has been the source of much frustration, and we consider that, especially given the price, it really should work better out of the box. If you can afford the asking price and get the lens functioning properly, you will certainly be delighted; but for most users we can't help but feel that the Sigma, or even the older FA 50mm F1.4, will be a better (and safer) option.
Rating (out of 10)
|Ergonomics & handling||8.5|
Recommended (with reservations)
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Pentax DA* 55 mm F1.4 SDM Review samples