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Canon EF-S 17-55mm f/2.8 USM IS - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortion
The EF-S 17-55mm f/2.8 USM IS exhibited average distortion figures for a lens in
this class. As expected there is relatively pronounced barrel distortion (2%)
at 17mm which evens out very shortly beyond. At 24mm there is already marginal
pincushion distortion which increases continuously towards the long end of the
zoom range (1.15%).
17mm:
24mm:
35mm:
55mm:
The chart above has a real-world size of about 120x80cm.
Vignetting
The EF-S 17-55mm is a reduced image circle lens and these lenses tend to
produce higher vignetting figures. Unfortunately the lens is no exception
to the rule. At f/2.8 the lens shows very pronounced vignetting around 1EV
at all focal lengths. Stopping down helps to reduce the problem and from
f/4 it's reasonably well controlled. However, it is a weak spot of this
lens.
MTF (resolution)
Unlike most other dedicated APS-C zooms the EF-S 17-55mm f/2.8 USM IS delivered
a very impressive performance throughout the zoom range. In fact the center
resolution of the lens is among the very best tested to date (incl. fix-focals)
and it probably exceeds the limits of the 8 MP sensor of the EOS 350D (used for
testing). The lens is also capable to deliver corner to corner sharpness though
there's (naturally) a little penalty at the image borders. However, even the
extreme corners stay in very good territory and stopping down helps
to lift the figures even further. There's a marginal drop in performance
at 55mm at f/2.8 but even here there's little to worry about.
The lens showed a slight degree of field curvature at 17mm.
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
Please pay attention to the new scale of [650,2150] which will be used for all EOS tests from now on.
Chromatic Aberrations (CAs)
Chromatic aberrations (color shadows at harsh contrast transitions) tend to be a weak spot
of most zooms in this range. However, the EF-S 17-55mm f/2.8 USM IS exhibited an
unusually moderate degree of border CAs well below the 1 pixel barrier even at the 17mm setting.
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