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Sigma AF 400mm f/5.6 HSM APO macro - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortion
As to be expected from a fix-focal lens and especially for a fix-focal the level of
distortion is absolutely 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 only
very little vignetting at f/5.6 which is hardly field relevant. From f/8 & up the issue
is negligible.
MTF (resolution)
The Sigma AF 400mm f/5.6 HSM APO macro proved to be a worthy representative of the
fix-focal lens league with very strong resolution figures across the tested aperture
range. The sweet spot of the lens is at f/8 where it achieves an excellent
center quality. Otherwise it's easily in very-good territory even at the borders.
Beyond f/8 diffraction is the limiting factor. It's interesting that the figures are
slightly superior to the Canon EF 400mm f/5.6 USM L.
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)
Typical for most tele fix-focals CAs (color shadows at harsh contrast transitions) are very low
and nothing to worry about under field conditions.
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