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Canon EF 24-70mm f/2.8 USM L - Review / Test Report - Analysis |
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Lens Reviews -
Canon EOS (APS-C)
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Page 2 of 3
Distortion
The level of distortion is very low for a standard zoom lens with
very slight barrel distortion at 24mm and marginal pincushion distortion
at 70mm. At 40mm there is no distortion at all. Really a great performance here for a zoom!
24mm:
40mm:
70mm:
The chart above has a real-world size of about 120x80cm.
Vignetting
On APS-C DSLRs vignetting is very well controlled with the lens.
Wide-open vignetting does not exceed ~0.5EV which is usually not much
of an issue in real life situations. One stop down the problem is
basically negligible.
MTF (resolution)
Well, I guess everybody has a nemesis and mine is the Canon EF 24-70mm f/2.8 USM L.
It took me 4 (f-o-u-r) samples of the lens to get a good one - please note: "good",
not a "great" sample. The first three variants showed rather hefty centering defects
which spoiled the results quite a bit.
This final sample exhibited a very good to excellent center resolution at wide-open
aperture throughout the tested focal length range. The borders follow on a good to
very good level. Stopping down lifts the center further into excellent territories
and the borders improve gradually till about f/5.6 to f/8. The sweet spot of the
lens is in the middle of the zoom range.
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
Lateral chromatic aberrations (CAs) can be visible at 24mm where the average
width exceeds 1 pixel at the image border. At the other focal length CAs are practically
negligible. All-in-all a very good characteristic for a standard zoom here.
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