Lens review

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

8. Vignetting

As far as the vignetting is concerned, the Tamron is the typical model in its class. The darkness in the corners of the frame is present for all the focal lengths and at the wide open aperture. This is probably the price for its small size and good aperture.

At 17 mm and f/2.8 the light fall off reaches 38% (-1.4 the value of the diaphragm). By comparison, the Sigma 17-70 mm and 18-50 mm values reach 40%, the Canon 17-55 mm is 41%, while the Nikkor 18-70 mm is as much as 50%. When stopping down the lens for Tamron, the vignetting decreases to 22% and at f/5.6 it drops to 18%. At f/11 focal length the vignetting reaches an acceptable value of 10%.

In the middle of the focal length range the situation is much better. At the f/2.8 the light fall off reaches 28% (-0.94 value of the diaphragm), at the f/4.0 it drops to 12%. Further on, for f/5.6 and more the vignetting is almost invisible.

At the end of the focal length range (at the 50 mm focal length and the wide open aperture) the vignetting reaches 33%. It drops quickly when we stop down the lens and at f/4.0 it is 14% and at f/5.6 it is only 8%.

We can say that in this category Tamron’s results are similar or slightly better than its competitors.