Tokina AF 16-50mm f/2.8 AT-X Pro DX (Nikon) - Review / Test Report - Analysis
Lens Reviews - Nikon / Nikkor (APS-C)

Distortion

At 16mm the lens shows fairly heavy barrel distortion (~3.55%) - this is slightly higher than average but then we're also talking about 16mm here rather than 17mm or 18mm. Beyond the extreme wide-end the distortion is actually very well controlled with slight barrel distortion at 24mm and slight pincushion distortion at 35mm and 50mm.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
16mm 24mm 35mm 50mm

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

Vignetting

The Tokina is a dedicated APS-C lens but thanks to its rather large front element vignetting is generally pretty well controlled. The weak spots are at 16mm @ f/2.8 (1.1EV) and less so at 50mm @ f/2.8 (0.74EV). At all other tested settings vignetting is not field relevant.

MTF (resolution)

The Tokina produced very high but also quite mixed resolution figures in the lab. At 16mm the center performance is excellent to absolutely superb whereas the border and corner performance is only good at f/2.8 and very good from f/4 onwards. The borders improve at 24mm and more so at 35mm and the center performance remains very high. At 50mm @ f/2.8 the border quality drops again although the center resolution stays on a very good level. Stopping down helps to recover the borders to very good figures at f/4 and excellent quality at f/5.6 and f/8. The general sweet spot of the lens is reached around f/5.6.

It is worth to mention that the lens suffered from a slight centering defect towards the long end of the zoom range. A fully valid sample may have a slightly better border performance at large apertures.

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)

CAs (color shadows at harsh contrast transitions) are the primary weakness of the Tokina. At 16mm @ f/2.8 the CAs peak way beyond 2.5px on the average at the image borders. Stopping down improves the problem quite a bit without resolving it. At longer focal lengths the CAs could still be better at f/2.8 but beyond from f/4 onwards it is generally well controlled. Due to the mentioned centering defect the CAs are quite uneven at 50mm.

Here's a 100% sample portion of a shot taken at 16mm @ f/8:

Flare

So far Tokina lenses had a rather bad reputation when it comes to strong contra light. However, the AF 16-50mm f/2.8 AT-X Pro DX seems to be reasonably resistant against flare. Here's a 100% sample portion of a shot taken at 38mm @ f/8:




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