Zeiss Vario-Sonnar T* 16-35mm f/2.8 ZA SSM ( Sony SAL-1635Z ) - Full Format Review / Test Report - Analysis
Lens Reviews - Sony Alpha (Full Format)
Article Index
Introduction
Analysis

Distortion

The Zeiss produces a strong degree of barrel distortion (~2.9%) at 16mm. The problem eases at 21mm (1.5%) and is basically gone at 28mm. At 35mm the distortion turns to a moderate pincushion type (~1%).

Move the mouse cursor over the focal length text marks below to observe the respective distortions
16mm 21mm 28mm 35mm

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

Vignetting

Full format DSLRs are very demanding regarding the vignetting characteristic of a lens. At 16mm even the mighty Zeiss struggles with an edge shading of more than ~2.3 f-stops (EV). It helps to stop down, of course, but the vignetting remains higher than 1EV even at f/11. To be fair this is rather typical for ultra-wide lenses though (the "natural" vignetting is already very high here). The problem isn't quite as hefty at 21mm and beyond but it is noticeable at large aperture nonetheless.

MTF (resolution)

The Zeiss produced a mixed resolution characteristic in this full format test scope. At 16mm it is easily among the very best lenses out there with an exceptionally high center quality and very good borders. The extreme corners are good at f/2.8 but even they reach very good levels at f/5.6 - the peak quality setting at 16mm. Diffraction effects aren't overly noticeable till beyond f/11. The center quality remains great at all other focal lengths but the border and corner quality suffers quite a bit here. At 21mm they're only "good" at f/2.8 and you should stop down to f/5.6 to reach very good results across the frame. The 35mm setting is clearly the weak spot with soft borders/corners at f/2.8. Stopping down to f/8 makes sense here.

The Zeiss produced some field curvature at 16mm in our APS-C test. However, the full format borders were pretty much in line with the center so there's only a "dent" in the focus field in the middle ground between the center and the corners.

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 within the full format test scope. They're comparable to the results of the APS-C test and as such very acceptable. We've seen a lot worse here in other full format tests.

Verdict

The Zeiss Vario-Sonnar T* 16-35mm f/2.8 ZA SSM didn't quite deliver as harmonious results as in the corresponding APS-C test but some aspects remain impressive. This is especially true for the resolution figures at 16mm which are easily among the best in this lens class. The lens struggles at large aperture settings at longer focal lengths but the peak performance (f/8-11) is very high. Lateral CAs are very well controlled. Barrel distortions can be disturbing at 16mm. The amount of vignetting is very high at 16mm/21mm @ f/2.8 but if you stop down it's not all that bad.

The mechanical quality of the lens is very high thanks to a tightly assembled combination of high quality plastic and metal parts. The SSM AF is both very fast and accurate and definitely a progress compared to the old screw-driven AF.

The Vario-Sonnar is an expensive lens and some may wonder whether it's really worth it - it's not a flawless lens after all but then no ultra-wide lens is. It's certainly capable of delivering great results if you're aware of its weaknesses and circle around them.

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