DSLR photographers looking to move up from the distortion and limited sharpness and speed of their kit lens will welcome this new wide-to-medium tele. Tamron has toted out big-gun technology for its 26-78mm equivalent ($450, street). This Di II (digital only) optic boasts a high speed, constant aperture, two aspheric elements, internal focusing, one element of low-dispersion glass, and another of a super low-dispersion XR (Extra Refractive Index) glass for, the company claims, better control of chromatic aberration.
HANDS ON: Overall weight and dimensions are about average and nearly identical to Sigma's comparable 18-50mm f/2.8 digital zoom ($409, street). This new lens offers few operational or cosmetic surprises. The zoom action is somewhat overdamped, almost obviating the need for the built-in zoom lock (at 17mm). With an especially tight turning radius, the focus ring makes for quick, if coarse, manual focusing. The lens' most distinguishing physical trait is its AF motor, which, while fast and smooth, emits a whine as it autofocuses.
IN THE LAB: SQF testing showed Excellent sharpness and contrast at three tested focal lengths -- while good, the numbers are about average by today's standards.
But, distortion control is clearly superior, especially at the wide end. At 17mm, DxO Analyzer 2.0 tests showed only Visible barrel distortion (0.42%) -- a significant improvement over Tamron's comparable 17-35mm f/2.8-4 zoom, which hasVery Visible barrel distortion at 17mm (2.1%). The longer focal lengths also earn well-above-average numbers: At 24mm, we found virtually no distortion (0.06% or Imperceptible pincushion) and, at 50mm, only Slight pincushion (0.14%). Bravo, Tamron.
With no detectable light falloff in the corners by f/5.6 at 17mm, or by f/4 at the longer focal lengths, the lens' vignetting characteristics are also commendable.
Its constant close-focusing distance of about 10 inches delivers a maximum magnification range from 1:8.8 at 17mm to 1:3.9 at 50mm-even more sexy numbers.
CONCLUSION: Shooters itching for a wide-angle upgrade will probably find relief with the quality and attractive pricing of Tamron's new multipurpose workhorse.
$750 cheaper than Nikon's comparable 17-55mm f/2.8.
$40 more expensive than the comparable Sigma.