Canon EF-S 18-135 mm f/3.5-5.6 IS STM
5. Chromatic and spherical aberration
Chromatic aberration
The tested lens doesn’t seem to have any problems with the longitudinal chromatic aberration as you can see in photos below.
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Still when it comes to the lateral chromatic aberration some issues become apparent and a graph below shows it well.
That aberration is the easiest to spot at focal lengths ranging from 18 to 35 mm - no matter what aperture you employ, its level is near 0.12% so a value we deem to be medium. At 70 mm the chromatic aberration becomes imperceptible but it increases once again at the maximum focal length. Still its level goes no higher than to the borderline between low and medium values.
It’s worth mentioning that this performance differs greatly from the one you saw in the case of this lens’s predecessor; that lens’s chromatic aberration highest level of almost 0.15%. was reached at 70 mm. It is actually another good argument that you deal here with a completely new optical construction.
To sum up for a zoom lens with such a multiplier these results are sensible and the aberrations, described above, won’t bother you in real life.
| Canon 50D, 18 mm, f/5.6 | Canon 50D, 70 mm, f/16.0 |
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Spherical aberration
We didn’t observe any focus shift effect so the tested lens can’t have a lot of problems with spherical aberration. That fact is additionally confirmed by defocused images of a diode which remain similar in front of and behind the focus.
| Canon 50D, 122 mm, f/5.6, in front of | Canon 50D, 122 mm, f/5.6, behind |
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