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Sigma AF 12-24mm f/4.5-5.6 EX DG HSM - Review / Lab Test Report - Analysis |
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Lens Reviews -
Nikon / Nikkor (APS-C)
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Page 2 of 2
Distortion
The Sigma shows a quite unique distortion characteristic for an ultra-wide angle
lens - it is extremely well corrected here with only minimal distortion even at 12mm.
The lens is basically free of distortion at 24mm. The remaining distortion is
slightly wavy in style though.
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Move the mouse cursor over the focal length text marks below to observe the respective distortion
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| 12mm |
17mm |
24mm |
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The chart above has a real-world size of about 120x80cm.
Vignetting
The Sigma is a full format lens thus enjoying a sweet spot advantage on APS-C DSLRs.
At 12mm vignetting is still quite pronounced although not excessive at f/4.5. At all
other settings the problem is very well controlled for such a lens.
MTF (resolution)
The Sigma AF 12-24mm EX produced very good resolution figures throughout the tested
aperture and focal length range. There're competing lenses with a better center
performance out there but the resolution characteristic is unusually even across
the APS-C image frame - even at the extreme borders at 12mm. A nice side effect
of the full format nature of the lens.
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)
The Sigma has not many weaknesses but it has definitely one - lateral CAs (color shadows at
harsh contrast transitions). At 12mm and 17mm CAs are quite extreme and not really acceptable
unless corrected via imaging tools (like most RAW converters). The CA situation is quite
good at the long end of the zoom range.
Verdict
The Sigma AF 12-24mm f/4.5-5.6 EX DG HSM is the most extreme full format ultra-wide zoom lens
around and it is still a "mainstream" ultra-wide lens when used on APS-C DSLRs. If you're looking
for a future-proof "duo-format" lens in this class - well, here it is. However, there're
a couple of further good arguments in favor of the lens. In the APS-C scope the resolution is
very high and even throughout the tested aperture and focal length range and as such more
harmonious compared to dedicated APS-C zooms which tend to suffer from edge problems.
Distortions are extremely well controlled for a lens in this class and vignetting is generally
not a problem except maybe at 12mm @ f/4.5. The only significant issue are lateral CAs at and
below 17mm - you better shoot RAW files and correct the issue in your RAW converter, otherwise
CAs are too extreme. The build quality of the Sigma is excellent and the fast and near-silent
HSM (ultrasonic) AF drive is a welcome feature. The price tag of the lens is fairly moderate
in relation to what you get for your bucks. Highly recommended ... if you can get a good sample
(the tested sample in Canon mount wasn't quite as good).
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