Zeiss Planar T* 85mm f/1.4 ZA ( Sony SAL-85F14Z ) - Review / Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)
Tuesday, 11 March 2008 09:44

Distortion

Typical for fix-focal length lenses in this range there're virtually no significant distortion to worry about (0.2%).

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

Vignetting

The Sony 85mm f/1.4 is a full format lens and as such enjoying the usual sweet spot advantage when used on an APS-C DSLR. Within this scope the lens shows a little vignetting at f/1.4 (0.5EV) but this isn't really something to worry about in field conditions. The problem is absolutely negligible by f/2.

MTF (resolution)

The Zeiss 85mm f/1.4 ZA produced superb resolution figures in the MTF lab. At f/1.4 the quality is already exceptionally high for such a lens and unlike e.g. the Sony 50mm f/1.4 the contrast level is perfectly usable. It's not really a primary aspect for such a lens but the center to border resolution is very even. Stopping down lifts the resolution level a little and the peak is reached around f/4. Interestingly the 50mm f/1.4 is a little sharper in the center but this is nit-picky.

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 very well controlled with an average pixel width around 0.4px at the image borders. Generally this is nothing to worry about.

Bokeh

The quality of the bokeh is naturally of major interest for an ultra-large aperture lens and the Zeiss does not disappoint here. Out-of-focus highlights show a circular shape from f/1.4 up to about f/2.8. At f/4 the shape deteriorates a little. There's basically no outlining effect here - this is about as good as it gets in lens land. The blur is very smooth and uniform. However, you may also notice the rather massive amount of longitudinal chromatic aberrations in the cards - more on this in the next chapter.

You can download the full-size images here:

Longitudinal (Axial) Chromatic Aberrations (LoCA)

LoCAs (non-coinciding focal planes of the various colors), sometimes called "bokeh CAs", can be a problem in the field. Similar the Canon 85mm f/1.2 USM L and Nikkor 85mm f/1.4 the Zeiss does also suffer from this optical defect. As you can notice below the halos have different colors - magenta (red + blue) in front the focus point and green beyond. The problem is rather pronounced at f/1.4. It decreases slowly the further you stop down but it is still visible at f/4. The Zeiss 135mm f/1.8 ZA is probably a little better here thanks to its 2 ED elements - the ZA 85mm f/1.4 is a more conventional design.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/1.4 f/2 f/2.8 f/4




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