Lens Test: Pentax 300mm f/4 SMCP-DA* ED IF SDM AF

One of Pentax’s top rated DA* (“DA star”) lenses, and a stablemate to the well-reviewed 200mm f/2.8, this 450mm equivalent ($1,300 street) is a digital-only prime for APS-sensored DSLRs. It incorporates O-rings and gaskets to repel moisture and dust, Pentax’s “Super Protective” SP coating that makes easy work of removing front-element smudges, and extra-low-dispersion glass for added sharpness. It also has the Pentax sonic-drive autofocus motor (SDM) that adds speed and cuts AF noise, but only on newer Pentax bodies (K100D owners will be disappointed). And it will accept Pentax’s discontinued S-series teleconverters.

HANDS ON: Wearing the same faint crinkle finish as the 200mm, this otherwise matte-black lens also sports the same green and gold accents. It has a removable tripod collar, gold depth-of-field scale, and extra-large, very well-damped MF ring. At more than 2.5 pounds and 10 inches long (with removable hood), it’s 2 inches longer and a pound heavier than the 200mm f/2.8, on par with some full-frame 300mm f/4s. It ships with a soft lens case and a large rubber-edged hood that has a clever finger window — a trap door that slides off to allow access to barrel-mounted filters.

IN THE LAB: SQF results were in the Excellent range, and images shot in the field were satisfyingly contrasty and sharp. DxO Analyzer 3.0.1 distortion-control tests found only Imperceptible pincushioning (0.05%), a fine showing. And we detected no vignetting in the corners, even at maximum aperture. The top magnification at the close-focusing distance of 53.75 inches was a powerful 1:3.76, significantly better than the 1:4.56 turned in by the 200mm DA* lens.

CONCLUSIONS: Easily handheld, and, with the hood reverse-mounted, conveniently carried in an average-sized camera bag, this very versatile tele will score high marks among nature and sports shooters — especially K20D, and K200D owners who can take advantage of that fast and quiet SDM AF motor.