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Canon EF 24-85mm f/3.5-4.5 USM - Review / Lab Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 2
Distortion
The lens shows some very strong barrel distortion at 24mm changing
to slight pincushion distortion at 50mm and 85mm.
24mm:
50mm:
85mm:
As usual you should probably expect more distortions towards closer focus distances.
Vignetting
The EF 24-85mm f/3.5-4.5 USM is a full frame lens so it can take advantage
of a sweet spot effect on APS-C DSLRs and it shows. Vignetting is basically
a non-issue with this lens at any focal length even at wide-open aperture.
MTF (resolution)
As hinted above the EF 24-85mm f/3.5-4.5 USM received some rather mediocre
reviews during the mid ´90s. However, all these reviews were based on
full frame analysis. When looking at the original Canon MTF figures the
lens is very good except at the borders. On APS-C DSLRs the borders
reside way beyond the cropping factor and this also shows up in the Imatest
measurements. On the EOS 350D the lens is capable to deliver a very good
to even excellent center performance combined with marginally worse
borders. Very impressive and basically as good as the pro-grade
EF 24-70mm f/2.8 USM L (again: just on APS-C DSLRs).
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
During the MTF analysis it became obvious that chromatic aberrations
(color shadows at harsh contrast transitions) are a weak spot of the
lens. At the image borders the problems almost reaches 2 pixels on
the average at 24mm at f/3.5. Quite bad. However, the issue decreases
rapidly towards medium aperture settings where the lens is more in line
with the rest of the gang. At 50mm the problem is still quite pronounced,
less so at 85mm.
Verdict
The Canon EF 24-85mm f/3.5-4.5 USM exhibited a quite mixed performance.
On the upside the lens is very sharp with very little vignetting throughout
the range. Unfortunately distortions at 24mm are pretty hefty as are chromatic
aberrations. The build quality is pretty decent and the AF performace is
a joy. All-in-all the lens is capable to beat the cheapo EF-S 18-55mm as well
as the EF-S 17-85mm IS and regarding sharpness it can even rival the the
EF 24-70mm f/2.8 USM L (on APS-C). If the focal length range was more attractive
here the lens would have been a killer but as such it is just a good
compromise.
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