Tamron AF 17-50mm F/2.8 XR Di-II LD SP ZL Aspherical (IF) Zoom Lens for Konica Minolta and Sony Digital SLR Cameras Decide Now

I bought a Tamron 17-50mm lens from Amazon last week for use on a Sony A200 and it arrived promptly in the mail, intact, though minimally cushioned in a small box. I put the lens through a series of tests around the yard, checking accuracy of auto focus, better aperture settings and resolution across the images.

The lens is very sharp--and even at the wider focal lengths, holds considerable resolution of the horizon at infinity right to the image margins. With the exception of the widest 17mm focal length, which had noticable corner softness (and extreme distortion) in forground elements (mostly fixed with apertures around F11), the lens produced sharp resolution right to the corners through the whole zoom range. There is very noticable distortion at 17mm, the distortion quickly diminishing at even slightly longer focal lenths on through the whole zoom range. I used mostly F8 for all the test shots.

The lens exhibits enough chromatic aberration right up through 24mm that not all of it can be removed with post processing. Between 17mm and 24mm, there is (with my copy of this lens) an excessive, odd chromatic stain, like a green tinted halo spreading well out beyond sharp or vertical edges, along with some ghosting of edges where light and dark meet--mostly evident on the left 1/3rd of the image frame. The green tint visible on the left side of images was wider than I've seen in any other lens and more substantial--and beyond repair. There is also a noticable greenish shift in image color toward both margins of a photograph, especially on the left side. This seemed consistent through most of the test shots, though it took me a while to notice it. This is not a characteristic of the camera, since another lens (a Sigma 24-60mm EX that also shows some similar, though less, chromatic tinting) does not produce any color shift at the image edges.

The Tamron 17-50mm is remarkably sharp and the auto focus is consistently accurate. It should be noted that the lens focus ring markings on my copy are not at all accurate through the entire zoom range for finding infinity focus--so auto focus accuracy is important. My disappointment with this lens is that the chromatic halos produced on the left side of the image at wider focal lengths are large enough to appear in large prints. There does seem to be a greenish shift in color toward the left and right margins of the images shot at the wider focal lengths (17-24mm). Guessing my purchase is just a less than perfect copy of the lens and I'm returning it.Get more detail about Tamron AF 17-50mm F/2.8 XR Di-II LD SP ZL Aspherical (IF) Zoom Lens for Konica Minolta and Sony Digital SLR Cameras.