Tamron AF 28-75mm f/2.8 SP XR Di LD Aspherical (IF) (Nikon) - Review / Lab Test Report - Analysis
Lens Reviews - Nikon / Nikkor (APS-C)
Article Index
Introduction
Analysis

Distortion

The Tamron 28-75mm XR exhibits a medium degree (~1.5%) of barrel distortion at its 28mm setting changing to minor pincushion distortion at 75mm (~0.4%). At 40mm distortion is marginal. A very decent performance for a standard zoom lens here.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
28mm 40mm 75mm

The chart above has a real-world size of about 120x80cm.

Vignetting

APS-C DSLRs such as the Nikon D200 take advantage of the sweet spot of full format lenses. In this scope the Tamron produced a very low degree of vignetting throughout the range and at all aperture settings.

MTF (resolution)

The resolution figures of the Tamron were generally very good to excellent but they were also spoiled by a centering defect which showed up at large-aperture settings specifically at the wide-end of the zoom range. Apart from this performance hit the center resolution of the tested sample was generally excellent and the borders can follow quite closely. Quite impressive for a lens in this price league.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

The lens exhibits a very decent degree of chromatic aberrations (color shadows at harsh contrast transitions). The average CA pixel width at the borders remain below 1 pixel throughout the tested range so the issue shouldn't be overly disturbing in field conditions.

Verdict

The Tamron AF 28-75mm f/2.8 SP XR (forgive me for using a shorter variant of the name ...) proved to be a very good lens in the lab. The resolution figures are among the highest tested among the standard zoom lenses - the center resolution is generally excellent and the borders follow closely on very good to excellent levels. The distortions are very low as is the amount of vignetting and even CAs are very well under control. Nonetheless it should be mentioned that this is the 2nd tested sample of this lens and both showed centering defects - this is worrisome. The build quality of the lens is decent but nothing to rave about. If you can live with the rather odd zoom range within the APS-C scope the lens is worth a deeper look - assuming you can get a good sample.

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