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Zeiss ZA Planar T* 85mm f/1.4 (SAL-85F14Z) on Sony NEX - Review / Lab Test - Analysis & Verdict |
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Lens Reviews -
Sony NEX
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Page 2 of 2
Distortion
Typical for fix-focal length lenses in this range there're virtually no distortions (0.2%).
The chart above has a real-world size of about 120x80cm. This chart has been taken from the original review on the A700. This characteristic cannot change on a new base camera.
Vignetting
The Sony 85mm f/1.4 is a full format lens and as such it is enjoying the usual sweet spot advantage when used on an APS-C camera. Within this scope the lens shows a lesser degree of vignetting at f/1.4 (0.9EV). This is actually higher than what we have seen in our A700-based test. Whether this relates to the sensor or a different tone curve is hard to tell. Such a light falloff is not extreme but certainly visible in critical scenes. The problem is basically negligible from f/2 onward.
MTF (resolution)
You may have seen the Sony EA-LA2 adapter on the first page of this review. However, for the lab tests we have actually used the EA-LA1 adapter which has no SLT mirror. There is a bit of a difference between the achievable quality between the two in the lab but this is rather irrelevant from a real world perspective.
Used the old A700 the Zeiss 85mm f/1.4 ZA produced superb resolution figures in the MTF lab but things are not all that simple anymore on the 24 megapixel sensor of the NEX 7. The center quality is still very fine at max. aperture but the borders can't quite follow here. However, they are still "good" anyway. There is already a substantial boost at f/2 resulting in a very good quality across the frame. The peak performance is reached between f/2.8 and f/5.6 with an excellent center and very good borders. Diffraction has a very slight (decreasing) impact at f/8.
Please note that the MTF results are not directly comparable across the different systems!
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 with an average pixel width around 0.8px at the image borders. Generally this is nothing to worry about albeit slightly higher than we expected.
Verdict
The Zeiss Planar T* 85mm f/1.4 ZA remains a very good lens on the NEX 7. However, even the mighty Zeiss isn't perfect anymore on the 24 megapixel sensor. At max. aperture the center performance is certainly very good but the border quality is a bit lower than expected. This is somewhat surprising considering the fairly big lens to sensor distance due to the required adapter. The decrease in border quality either relates to a difficult sensor characteristic or, possibly, to a sub-optimal sample of the lens. Regarding the typical applications at max. aperture the border qualities are not overly relevant anyway. Starting at f/2 the delivered quality is also pretty impressive across the frame. The vignetting at max. aperture is somewhat on the high side on the NEX 7. Distortion and lateral CAs are basically non-issues from a field perspective. The quality of the bokeh is generally smooth and buttery but bokeh fringing is very pronounced at large aperture settings. That's a fate the Zeiss shares with comparable lenses such as the Canon EF 85mm f/1.2 USM L.
Thanks to an all-metal body the lens feels very solid. If you're nit-picky you may criticize the focus ring which shows a little play when changing the focus direction. The AF speed (via EA-LA2) is fine although nothing to rave about. At around 1400EUR/US$ the Zeiss ZA 85mm f/1.4 isn't cheap for sure but definitely worth it considering its optical qualities. The handling is quite fine on the Sony NEX when using the EA-LA2 although the positioning of its mirrorbox (on the adapter) is less than perfect. However, the size advantage of the NEX system is certainly gone in any case so the Zeiss lens may not be an obvious choice here.
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