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Tamron SP AF 17-50 mm f/2.8 XR Di II LD Aspherical (IF)

27 September 2007
Robert Olech

6. Distortion

Unfortunately, the savings on aspherical glasses did not have good results in this category either. For Tamron 28-75 mm we have four aspheric elements and the distortion at wide angle was at the –1.62% level. For the 17-50 mm model (two aspherical elements) for 17 mm focal length, the clear barrel distortions are twice as big and reach a level of –3.7%.

Tamron SP AF 17-50 mm f/2.8 XR Di II LD Aspherical (IF) - Distortion


How does this result look in comparison with the competition? When we compare it with really expensive models, like the Canon 17-55 mm f/2.8, the results are weak. The Canon’s distortion was –2.5%. If we compare the Tamron with something at the same price range, the Tamron looks much better. The Canon 17-85 mm IS USM has a much higher distortion of –5.7%, the Sigma 17-70 mm has -4.0% and the Nikkor 18-70 mm has -4.5%.

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When the focal length is increasing the problem of geometrical distortion starts to decrease. For 30 mm the distortion is almost invisible (0.24%) and at 50 mm is only 0.97%.

Tamron SP AF 17-50 mm f/2.8 XR Di II LD Aspherical (IF) - Distortion

Tamron SP AF 17-50 mm f/2.8 XR Di II LD Aspherical (IF) - Distortion