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Zeiss Planar T* 85mm f/1.4 (Contax N to Canon EF) - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortion
The Zeiss T* 85mm f/1.4 produces a negligible degree of distortion (~0.2%) which is
not field-relevant.
The chart above has a real-world size of about 120x80cm.
Vignetting
The Zeiss lens exhibited the typical vignetting characteristic for full frame, ultra-large
aperture tele lenses used on an APS-C DSLR. At wide-open aperture the vignetting is
moderate at around 0.7EV. Starting at f/2 the problem is negligible under field conditions.
MTF (resolution)
The Zeiss lens showed impressively high resolution figures although it does not
match the EF 85mm f/1.2 USM L here. The center performance is already very good
at f/1.4 and excellent beyond. However, the border quality isn't quite on that
level specifically at large apertures. At f/1.4 the borders are fairly soft and
stopping down does gradually improve the resolution figures to very good
levels by f/2.8 and up to an excellent peak 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)
Chromatic aberrations (color shadows at harsh contrast transitions) are
very moderate with an average pixel width around 0.3px at the image borders.
This is not field-relevant.
Typical for many ultra-large aperture lenses the Zeiss also shows some
Longitudinal Chromatic Aberrations (LoCA) resulting in greenish and reddish
out-of-focus edge transitions.
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