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Laowa 15mm f/2 FE Zero-D (Sony FE) - Review / Test Report - Analysis |
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Lens Reviews -
Sony Alpha (Full Format)
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Page 2 of 3
Distortion
Laowa advertises the 15mm f/2 as "Zero-D" or "Zero Distortion" lens. That's not quite true but at just 1.4% the amount of barrel distortion is very low indeed in this lens class.
Vignetting
Ultra-wide lenses tend to produce a lot of vignetting on full format cameras thus it's no surprise that the Laowa is also affected with a max light falloff of 3.3EV (f-stops) at 15mm f/2. Stopping down helps a bit but it remains a visual issue even at f/8. Due to the lack of electronic coupling (no EXIF data), there's also no way to use digital auto-correction to compensate for this.
MTF (resolution)
The Laowa 15mm f/2 FE Zero-D can produce good sharpness but it clearly has its issues as well. These are most obvious at large aperture settings. The center quality is excellent at f/2 already and the near-center performance is also perfectly fine. However, the outer image field is soft. The improvement at f/2.8 is rather marginal in the corners. Stopping down to f/4 does finally boost the quality. The broader center zone is very sharp and the borders are lifted to good levels. The corners are still not great here but usable at least. The peak performance is reached between f/5.6 and f/8 with good to very good borders and, finally, good corners. Diffraction has a higher impact from f/11.
The centering quality of the tested sample was Okay. The field curvature is comparatively low.
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 the image borders) are quite low with an average CA pixel width of 1.3-1.5px at the image borders. While you may notice traces of CAs in certain situations, it's usually not overly disturbing.
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