Best lenses for Pentax K-3: Recommended wide angle, telephoto and standard lensesBy Kevin Carter - Tuesday January 07 2014 Lens Recommendations
The highly regarded smc DA* 55mm f1.4 is the equivalent to a 85mm on the Pentax K-3 and, even as the most expensive listed, it’s not really surprising to see this ultrasonic-type (SDM) equipped AF lens sit at the top of the moderate telephoto rankings. At $249 the smc D 50mm f1.8 in second place looks promising in terms of optical quality but it lacks some of the refined features of the DA* 55mm f1.4 including the sonic AF motor, weatherproofing, and the nano-tech Aero Bright coating.
Sharpness at f1.4 isn’t high, but depending on your point of view, that’s probably a good thing for a portrait lens. Center sharpness is good at f1.8, better than the smc DA 50mm 1.8, and is slightly better throughout the aperture range, with the corners on both being a far way behind. Best uniformity is achieved at f2.8, though corners can’t quite match the centers for sharpness, which is true for both models. Despite the higher peak sharpness of the DA 50mm f1.8, the DA* model has the better overall performance.
In third place is the diminutive smc DA 70mm f2.4 Limited. It’s the equivalent to a 105mm but the compact ‘pancake’ design is highly attractive, measuring just 1.0” (25mm) in length and weighing 4.6 oz (147g). It’s not bitingly sharp at maximum aperture but it does have good sharpness centrally. Sharpness and uniformity improve on stopping down, as you might expect, where at f4 the corners are almost up to the center. The corners start falling behind again though at f5.6. However, corner sharpness isn’t really a big issue for most portrait lenses.
The only zoom in this category we’ve tested is the full-frame Tamron SP AF 28-75mm f2.8 XR Di LD Aspherical (IF). It’s great value and has very good image quality, at least centrally, even at the longer end from f4 onwards. Vignetting, distortion and chromatic aberration are all low, too.