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Zeiss Distagon T* 21mm f/2.8 ZF (DX) - Review / Test Report - Analysis |
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Lens Reviews -
Nikon / Nikkor (APS-C)
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Page 2 of 3
Distortion
The lens shows moderate barrel distortion of around 1.6%. This can be visible and disturbing for subjects with straight lines near the image border. However, the distortion is almost uniform and thus easy to remove in post processing.
The chart above has a real-world size of about 120x80cm.
Vignetting
Wide open the lens shows moderate light fall-off towards the corners of around 0.8 EV. Stopped down to f/4 and beyond, vignetting is no longer field-relevant.
MTF (resolution)
The lens delivers impressive sharpness across the whole frame at all tested apertures.
Center and border sharpness is excellent at any aperture, from wide open down to f/11 (where diffraction already reduces resolution). The corners follow only slightly behind with very good sharpness.
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 CAs (color shadows at harsh contrast transitions) are very well controlled at less than 0.4px on the average at the image borders. This is pretty much negligible in field conditions.
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