Zeiss Vario-Sonnar T* 16-80mm f/3.5-4.5 ZA DT ( SAL-1680Z ) - Review / Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)

Distortion

The Zeiss is a 5x zoom and as such subject to quite high distortion just like the rest of the gang. At 16mm there is heavy barrel distortion (~3.2%). Beyond 16mm the situation eases significantly with only slight barrel distortion at 24mm and slight pincushion distortion at 40mm and 70mm.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
16mm 24mm 40mm 80mm

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

Vignetting

Besides high barrel distortions the lens has a 2nd weakness - vignetting at 16mm @ f/3.5. At 1.4EV this is a little bit more than expected from a lens in this price league. From f/5.6 onwards the situation is good for a moderate ultra-wide setting. At the other settings the vignetting is relatively well controlled within its dedicated APS-C scope.

MTF (resolution)

The Zeiss produced very good to excellent resolution figures in the MTF lab. The center resolution is nothing short of stunning at all focal lengths and apertures. At 16mm the extreme borders are "only" good at f/3.5 but the quality increases significantly when stopping down to f/5.6. The local sweet spot is at f/8 with excellent borders and very good extreme borders. The situation is similar at 24mm. At 40mm and 80mm the border quality increases further to very good levels at f/4.5 and excellent levels by f/5.6. All in all very impressive.

Some of you may be a bit surprised that the naked LW/PH numbers did not increase between the former test based on the Alpha 100 and this one based on the Alpha 700. This originates in the differences of the underlying RAW-converters (ACR 3.7 for the Alpha 100 vs ACR 4.3/LR 1.3 for the Alpha 700).

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)

Lateral chromatic aberrations (color shadows at harsh contrast transitions) are well controlled at and beyond 24mm. However, at 16mm things aren't that rosy with an average CA pixel width of around 1.7px at the image borders. This can be disturbing in field images.

Bokeh

The Zeiss is a rather slow speed lens and the bokeh (the out-of-focus blur) is therefore usually quite underdeveloped. However, the lens does a fairly decent job here despite its aspherical element (which often means trouble within this scope). There's a bit of outlining visible in out-of-focus highlights but it's not too obvious. The blur is quite uniform and not overly nervous.

You can download the full-size image HERE.




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