LensTip.com

Lens review

Sigma A 18-35 mm f/1.8 DC HSM

18 June 2013
Arkadiusz Olech

5. Chromatic and spherical aberration


Chromatic aberration

The longitudinal chromatic aberration is not corrected in a perfect way – it makes itself felt at the maximum relative aperture which can be seen very well in the crops below.

Sigma A 18-35 mm f/1.8 DC HSM  - Chromatic and spherical aberration



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The cast of defocused images is not very distinct, though, so it would be difficult to call this aberration a serious issue.

Similar or even better things can be said about the lateral chromatic aberration. A graph below presents the values of that aberration for particular focal lengths.

Sigma A 18-35 mm f/1.8 DC HSM  - Chromatic and spherical aberration

At both ends of the focal spectrum this is not a problem, remaining negligible at 35 mm, low at the widest angle, only momentarily approaching the medium level. In the middle of the range the aberration can be a bit problematic because there it firmly reaches medium levels. Still if you want to be honest you have to admit that it is closer to low than to high values.

Sigma A 18-35 mm f/1.8 DC HSM  - Chromatic and spherical aberration

Spherical aberration

Already the first photo in this chapter shows that the spherical aberration shouldn’t be very problematic because there is no focus shift at all. Our conclusions are proven by images of defocused light points which, although showing a lot of fine, concentric rings, don’t differ from each other a lot.

Sigma A 18-35 mm f/1.8 DC HSM  - Chromatic and spherical aberration