Tokina AF 28-70mm f/2.8-2.6 AT-X Pro II - Review / Lab Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)
Article Index
Introduction
Analysis

Distortion

The lens shows a medium degree of barrel distortion at 28mm changing to marginal barrel distortion at 40mm and slight pincushion distortion 70mm.

28mm:

40mm:

70mm:

Vignetting

The AF 28-70mm f/2.6-2.8 AT-X Pro II is a full frame lens so it can take advantage of a sweet spot effect on APS-C DSLRs. Vignetting is no major issue in all but the most critical situations even at wide-open aperture.

MTF (resolution)

The Tokina exhibited very good resolution figures under lab conditions. At 28mm the center resolution is excellent straight from the max. aperture setting. The border quality isn't quite as high but still on a good to very-good level.

At 40mm the center quality remains on a very high level and the borders catch up significantly with excellent figures from f/5.6 and up.

There's a slight performance drop at 70mm specifically at f/2.8 where both the center as well as the border quality is very good. The local performance peak is at f/5.6 where both the center as well as the borders are excellent again.

The tested sample exhibited an off-coplanar projection (centering defect). According to Christian (owner) the lens is quite soft at very close focus distances at 70mm which may be a side effect of the defect.

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

Chromatic aberrations (color shadows at harsh contrast transitions) vary quite a bit according to the chosen focal length. At 28mm the problem correlates to the chosen aperture - at f/2.8 the issue is marginal but it increases to quite critical levels at medium aperture settings with a max. of 1.87 pixel on the average at the image borders. At 40mm and more so at 70mm the issue is quite a bit less pronounced.

Verdict

The Tokina AF 28-70mm f/2.6-2.8 AT-X Pro II was indeed able to beat the performance figures of its successor - the AF 28-70mm f/2.8 AT-X Pro SV. Probably not really surprising because the lens was also quite a bit more expensive at the time. Generally the lens produced pretty impressive results specifically regarding resolution. The level of distortions is quite moderate for such a lens and the vignetting figures are very low. On the other hand CAs can reach a disturbing level at 28mm at medium aperture settings. The build quality of the lens is, in principal, exceptional and as good as the very best genuine brand products here. Unfortunately the imperfect AF/MF switch mechanism doesn't really fit into the otherwise brilliant mechanical implementation.

Optical Quality:    
Mechanical Quality:
Price/Performance:discontinued
      
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