Zeiss Distagon T* 21mm f/2.8 ZF (DX) - Review / Lab Test Report - Analysis
Lens Reviews -
Nikon / Nikkor (APS-C)
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The lens shows moderate barrel distortions 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.
Wide open the lens shows pronounced light fall-off towards the corners of almost 1 EV. Stopped down to f/4 and beyond, vignetting is no longer field-relevant.
The lens delivers impressive sharpness across the whole frame at all tested apertures.
Center sharpness is excellent at any aperture, from wide open down to f/11 (where diffraction already reduces resolution). The borders and corners follow only slightly behind with very good sharpness.
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
Chromatic Aberrations (CAs)
Lateral CAs (color shadows at harsh contrast transitions) are well controlled at less than 0.9px on the average at the image borders wide open, reduced to 0.65px at f/11. This is pretty much negligible in field conditions.
Full size sample images are available in our FX review of this lens.
VerdictThe Zeiss Distagon T* 21mm f/2.8 ZF is a legendary lens, and in this review it certainly shows (again) why. The sharpness is impressive at any aperture and across the whole DX frame. Lateral CAs are quite low and as such contributing to the high resolution perception. Vignetting and distortion are also well controlled and not a field-relevant issue for most subjects.
Just like the rest of its family, the Zeiss lens is built to the highest standards. Some users may complain about the lack of AF but the focus confirmation is available in the viewfinder and in very critical (for example close focus) scenes Live-View can give you a helping hand. That said, it remains a bit of an anachronism these days. The price level is no doubt quite steep and due to the fact that it's an ultra wide FX lens, while on DX it only resembles a moderate wide angle lens.
Nonetheless: all-in-all highly recommended!