Zeiss Planar T* 85mm f/1.4 ZF (ZE) (on Canon EOS) - Lab Test / Review - Analysis
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Distortions

The Zeiss ZF T* 85mm f/1.4 produces an absolutely negligible degree of distortion (~0.1%).

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

Vignetting

The Zeiss lens exhibits the typical vignetting characteristic for an ultra-large aperture tele lenses used on an full format DSLR. At wide-open aperture the vignetting is high at ~1.7EV and still a bit visible at f/2. The problem is negligible from about f/2.8 onwards.

MTF (resolution)

Ultra large aperture lenses tend to struggle on full format DSLRs but the Zeiss lens is actually a bit better than similar lenses here. The center quality is already very good at f/1.4 and the borders/corners reach good levels (albeit just). The contrast could be better though especially in close focus scenarios. There's a substantial boost in quality at f/2.8 with an excellent center and very good borders/corners. The peak performance is reached around f/5.6. The quality is about as good as it gets here.

Below is a simplified summary of the formal findings. The chart shows in 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)

Chromatic aberrations (color shadows at harsh contrast transitions) are relatively well controlled although we've seen better lenses in this class here. The average CA pixel width at the image borders varies between 0.8px and 1.4px. This may be visible upon closer observation but it's actually not really something to worry about either.

Bokeh

The bokeh (quality of the out-of-focus blur) is generally very good. Out-of-focus highlights are very evenly rendered. At large apertures the discs deteriorate to a "cat's eye" shape towards the image borders but that's a rather normal behavior in this lens class. The blur is pretty smooth in the focus transition zones although the Canon EF 85mm f/1.2 USM L II is still be a tad better here especially with respect to the foreground blur.

Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)

The Zeiss lens shows very pronounced LoCAs at large apertures - this is, again, typical for such lenses. These green/purple halos in the focus transition zones are very obvious at f/1.4 and f/2. There're still some fringing hints at f/2.8 although that's not overly field relevant anymore.

You may also notice the focus shift (RSA) when stopping down from f/2 to f/2.8.

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

Verdict

Zeiss Z-series lenses are controversial beings because they lack auto-focus. However, Zeiss is a legendary brand name and some lenses do live up to this reputation - the Planar T* 85mm f/1.4 does qualify here - mostly at least. The lens is capable of producing bitingly sharp results when stopped down a little. The vignetting characteristic is about typical for a lens in this class. Distortions are a non-issue. The quality of the bokeh is very good although its direct competitor, the Canon EF 85mm f/1.2 USM L II, still has an edge here. However, there're also has a few weaknesses. The Zeiss lens shows a somewhat "dreamy" contrast characteristic at f/1.4. Whether this is a bug or a feature is a matter of application - portrait photographers will like it whereas still-life photographers probably won’t. Typical for ultra-large aperture lenses there's also some degree of purple fringing at large aperture. Due to the large front element the T* 85mm f/1.4 isn't quite as resistant against flare as its (Zeiss) cousins but certainly not worse than comparable lenses.

The build quality is also exceptionally high and a reminiscent of times when plastics were not the dominant form of mechanical design. The price tag of the Zeiss comes almost as a surprise - at 1100 €/US$ it costs quite a bit less that the Canon EF 85mm f/1.2 USM L (~1800EUR/US$) - so a deeper thought may not be as bizarre as it seems if you're shopping in this lens class.

Optical Quality:    
Field Quality:Portrait Photograohy)
Mechanical Quality:
Price/Performance:
      
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