Canon EF 24-70 mm f/4L IS USM
5. Chromatic and spherical aberration
The crops below, taken at 70 mm focal lengths by f/4.0 and f/5.6 apertures, show clearly that the tested lens doesn’t have practically any problems with correcting the longitudinal chromatic aberration.
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Also the lateral version shouldn’t cause any problems here. The graphs shown below present the performance on the edge of the APS-C sensor and on the edge of full frame.
The middle of the focal range fares the best – you can’t notice any aberrations there. The worst situation can be observed at the wide angle where the aberration doesn’t depend on the aperture, keeping a level of about 0.08%. Still it is not a big problem as it is a value on a borderline between low and medium levels.
If you remind yourself that the 24-105L had maximum results of 0.14% and the 24-70 mm f/2.8L II fared even worse, with the result of 0.17%, once again it is easy to answer why you might get interested in the 24-70 mm f/4L model instead.
| Canon 5D III, 45 mm, f/4.0 | Canon 5D III, 24 mm, f/11 |
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Spherical aberration
It seems that the Canon EF 24–70 mm f/4L IS USM experiences some spherical aberration problems. The first photos in this chapter show that when you pass from f/4.0 to f/5.6 the depth of field moves towards longer distances. It is not a huge effect but still noticeable.
Also the appearance of the light circles leaves a bit to be desired. The circle in front of the focus has a light centre surrounded by a much darker area which turns into a light rim. The image behind the focus is exactly the opposite of that. Instead of a rim you get a soft edge which turns into a light circle with a dark centre. If the spherical aberration was corrected properly you wouldn’t have noticed any of the effects, described above.
| Canon 5D MkIII, 45 mm, f/4.0, in front of | Canon 5D MkIII, 45 mm, f/4.0, behind |
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