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Sigma AF 105mm f/2.8 EX DG macro - Review / Lab Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 2
Distortion
As to be expected from a fix-focal lens and especially for a macro lens the level of distortion
is quite negligible.
The chart above has a real-world size of about 120x80cm.
Vignetting
On the EOS 350D with its reduced format (APS-C) the (full format) lens exhibits very little vignetting
at f/2.8 and infinity focus. From f/4 & up it is pretty much negligible.
MTF (resolution)
Typical for most macro lenses the Sigma AF 105mm f/2.8 EX DG macro performed very good to excellent
in the lab. The lens is already very good in the center at wide-open aperture with marginally worse
corners. The lens reaches its peak performance at f/8 with excellent results. As usual diffraction
is the limiting factor at smaller aperture settings. At f/22 the quality is still acceptable but
you shouldn't go beyond (f/45 is possible).
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)
Similar to most other fix-focal lenses chromatic aberrations (color shadows at harsh contrast
transitions) are exceptionally low and nothing to worry about.
Verdict
The Sigma AF 105mm f/2.8 EX DG macro is an excellent lens without any significant flaw.
It's optically as good as the Canon EF 100mm f/2.8 USM macro. The lens has a very good
build quality though not quite as nice as the Canon due to its focus extension system
and the conventional AF drive. However, the price tag is also lower so if you're on a
budget the lens is certainly worth a deep thought (as is the Tamron AF 90mm f/2.8 SP).
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