Zeiss APO Sonnar T* 135mm f/2.0 ZF.2 (DX) - Review / Test Report - Analysis
Lens Reviews - Nikon / Nikkor (APS-C)
Article Index
Introduction
Analysis

Distortion

On DX, the Sonnar produces a tiny amount of pincushion distortion. At 0.15% it is so low that in practical terms the lens can be considered distortion-free.

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

Vignetting

Since it is designed for the bigger area of a FX sensor, the Zeiss shows only moderate vignetting wide open, which as usual is reduced to lower numbers by stopping down. From f/4 onwards, light fall-off towards the corners is no longer noticeable.

MTF (resolution)

The resolution figures of the lens are stunning and on an exceptionally high level. Straight from the maximum aperture, the Sonnar delivers excellent resolution not only in the image center, but across the whole frame.

At smaller apertures the MTF numbers increase to even higher values. Theoretically the peak performance is reached at f/4. Practically, however, the sharpness is on such a high level at any aperture setting between f/2 and f/8 that there is no visible difference.

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 CAs (color shadows at harsh contrast transitions) are well controlled with low amounts of around 0.4 to 0.6 pixelsl on the average at the image borders.

Bokeh

The lens not only delivers outstanding sharpness, it also combines it with very pleasant bokeh.

Image blur is very smooth both in front of as well as behind the focal plane. In addition, background highlights are evenly filled and show almost no outlining. Typical for such a fast lens however, the highlights show a little bit of a cat's eye shape at the image borders at large apertures due to mechanical vignetting.

Bokeh Fringing

Bokeh fringing (non-coinciding focal planes of the various colors) is a common issue with relatively fast glass. It is usually visible as halos of different colors - magenta (red + blue) in front of the focus point and green beyond. Unlike lateral CAs, bokeh fringing cannot easily be fixed in post processing.

The Zeiss is an APO lens though, which means it corrects most of these colour shifts. As can be seen in the images below, there is only a minor amount of colour casts visible at f/2 that disappears completely by stopping down.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/2 f/2.8 f/4 f/5.6 f/8.0

Sample Images

You can find some sample images taken with the Nikon D3x in our Nikon FX review of the lens.

Verdict

The Zeiss APO Sonnar T* 135mm f/2.0 is outstanding and no doubt one of the best lenses we have had in the lab. Sharpness is amazingly high, distortion and CAs are very low, vignetting present wide open, as to be expected from such a fast lens, but not an issue stopped down. Bokeh is very smooth and on top of all that, it's an APO lens, so bokeh fringing is not an issue either.

The lens delivers images with high contrast, and as another pleasant surprise handles backlight extremely well and rarely shows signs of flare.

Mechanically, there is nothing to complain about, the lens is extremely solid and a pleasure to use. The ZF.2 variant doesn't provide weather sealing, however the updated Milvus variant does, at a price, though, literally.

There is no doubt that the Zeiss deserves our highest score of 5 stars as well as the "Highly recommended" rating. Now if only it had AF...

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