The HD PENTAX-D FA* 70-200mm f/2.8 ED DC AW plays a leading role in the company’s K-mount lens line-up. Photographers who favor shooting with prime lenses pretty much all of the time often feel that a 70-200mm f/2.8 is the most essential zoom, and you’ll find one in the kit back of most serious shooters. At the telephoto end of Pentax’s set of trinity f/2.8 lenses, the 70-200mm is the only one to earn a star, the ‘*’ being reserved for the company’s very finest optics, most of which are prime lenses.
Mount: Pentax K
Full frame: Yes
Lens construction: 19 elements in 16 groups
Angle of view: 34.5-12.5 degrees
Diaphragm blades: 9
Minimum aperture: f/22
Minimum focusing distance: 1.2m
Maximum magnification ratio: 0.13x
Filter size: 77mm
Pentax has packed plenty of features into this lens. Kicking off with the high-tech optical path, the design includes four SD (Super-low Dispersion) elements, two ED (Extra-low Dispersion) elements and two top-grade Super ED elements, the last of which have similar properties to fluorite glass in combating chromatic aberration. A combination of nano-structure Aero Bright Coating II and multi-layer HD Coating is applied to keep ghosting and flare to a minimum. A Super Protect coating is also applied to the front element.
Autofocus is pretty swift and very quiet, based on a DC (Direct Current) motor and features Pentax’s ‘Quick-Shift Focus System’. This enables full-time manual override of autofocus and comes with a three-position switch that gives priority to autofocus or manual override, as well as fully manual focusing.
The lens lacks optical image stabilization and, while it’s true that Pentax DSLRs feature in-body stabilizers, competing manufacturers often add optical stabilizers to their telephoto lenses, as it can further enhance effectiveness.
Overall performance is good with refined handling and the autofocus system works well. Extensive weather-seals ensure that you can keep shooting even when the going gets tough. Sharpness proved very impressive in our real-world tests but, for relatively short-range lab testing, edge-sharpness was poor and only the very central region of the image frame was impressively sharp when shooting wide-open at f/2.8.
We run a range of lab tests under controlled conditions, using the Imatest Master testing suite. Photos of test charts are taken across the range of apertures and zooms (where available), then analyzed for sharpness, distortion and chromatic aberrations.
We use Imatest SFR (spatial frequency response) charts and analysis software to plot lens resolution at the center of the image frame, corners and mid-point distances, across the range of aperture settings and, with zoom lenses, at four different focal lengths. The tests also measure distortion and color fringing (chromatic aberration).
Levels of sharpness are generally very good but in our close-range lab tests, edge-sharpness proved pretty poor and only the central region of the frame was really crisp at f/2.8, throughout the entire zoom range.
Color fringing is quite minimal, even towards the extreme corners of the image frame but can be a little noticeable if uncorrected.
Barrel distortion is can be noticeable at 70mm but is easy to correct but there’s very little distortion in the 100-200mm sector of the zoom range.
Typical of 70-200mm f/2.8 zoom lenses for full-frame DSLRs, this Pentax is no lightweight, and it’s heavier than most at 1,755g. With a ‘Star’ status usually reserved for Pentax’s top notch prime lenses, it aims to deliver excellent image quality, along with pro-grade build quality and excellent performance. It lives up to its claims in most respects but edge-sharpness could be better when shooting at close range.