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Canon EF 28mm f/1.8 USM - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortions
The lens showed a slight to moderate degree of barrel distortions (1.2%). Not stellar but
pretty good.
The chart above has a real-world size of about 120x80cm.
Vignetting
On an APS-C DSLR the EF 28mm f/1.8 USM enjoys a sweet spot effect here and
at 0.55EV vignetting is very low for such a large aperture lens. This is
already very acceptable for the vast majority of field situations. If
needed the issue can be basically completely eliminated when stopping down
to f/2.8.
MTF (resolution)
Similar to the Sigma AF 30mm f/1.4 EX the Canon lens showed a rather mixed behavior
in the lab. The center performance is already high straight from the max. aperture
setting peaking in exceptional resolution figures around f/4. Unfortunately the border
resolution lacks quite a bit behind. At f/1.8 the borders are very soft. Stopping
down help to gradually improve the resolution but even at f/8 the quality does merely
exceed very good values. At f/1.8 the lens also suffers from low contrast.
This is slightly disappointing for a modern fix-focal lens.
The resolution chart has been revised to take field residual spherical aberrations into account.
Below is a simplified summary of the formal MTF findings. The chart shows in line widths
per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to
know more about it you may check out the corresponding
Imatest Explanations.
Chromatic Aberrations (CAs)
CAs (visible as color shadows at harsh contrast transitions) can reach an average CA pixel width
of more than 2 pixels at the image borders - a very weak performance here. CAs can be reduced
and usually even eliminated via imaging tools but a fix-focals should definitely perform better
than that.
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