The Pentax SMC DA* 55mm f1.4 SDM lens was introduced in September 2008 to provide APS-C crop-frame camera users with a prime portrait lens. (DA* is Pentax's designation for crop-frame lenses.)
The lens equates to an 82.5mm lens on a full-frame camera, and it offers a wealth of goodies and some superb optics. But this comes at a price, and the question has to be asked: Is the lens worth it?
Pros
- Great optics, especially for its designated portrait role
- Excellent and durable build quality
Cons
- Extremely expensive
- Slow autofocus, which is also sometimes very inaccurate
Pentax SMC DA* 55mm f1.4 SDM Lens Review
This is a solid and well-built lens, designed for serious users of Pentax's crop-frame cameras. It's aimed at photographers wanting to shoot classic head and shoulders portraits. But, with its hefty price tag, will users be better off looking at third-party alternatives, such as the Sigma 50mm f1.4 EX DG lens?
Build Quality
You really can't fault the build quality of this Pentax lens. It's reassuringly solid, with a rubber seal around the lens mount to provide complete weatherproofing. The front element is recessed into the lens barrel, and it does an excellent job of preventing lens flare. The manual focusing ring is wide and easy to grasp. The lens even comes with an excellent lens hood, complete with a ring of rubber around its front to protect it from shock.
Autofocus
The lens has a built-in ultrasonic type motor, which is extremely quiet but is noticeably slower than its predecessors (which had screw-drive focus coupling). It should also be noted that these lenses won't work on Pentax cameras predating the K10D of late 2006.
Unfortunately, the autofocus is just not that accurate, and it is prone to problems. In all incidents, the lens required AF adjustment to be applied in camera. (AF adjustment is a feature of some Pentax cameras.) On the K-7 body where I tested it, the lens front-focused ever so slightly. However, I have heard reports that it will rear-focus on other, older camera models. It's not a major issue if you have AF adjustment, but it is time consuming and fiddly to get consistently sharp images ... and that's not what you want from a lens.
Optics
While the lens is a little soft wide-open, you only need to stop down fractionally to achieve excellent results. You'll receive the most consistent focus results between around f5 and f8, and the lens is at its absolute sharpest at f5. There's hardly any chromatic aberration with this lens, and distortion is practically non-existent. As a portrait lens, it's pretty brilliant optically!
In Conclusion
This is a tricky lens to rate. When it works, it's one of the best portrait lenses on the market. But the issues with its autofocus take far too much time and energy to deal with, and the lens is extremely expensive.
I would recommend it to Pentax users, because its optics are so good, but I urge caution if you're the kind of photographer who doesn't have the time or inclination to set it up for optimum use in the first place!