Sigma AF 400mm f/5.6 HSM APO macro - Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)

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.

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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