LensTip.com

Lens review

Pentax HD DA 20-40 mm f/2.8-4.0 ED Limited DC WR

8 February 2014
Arkadiusz Olech

5. Chromatic and spherical aberration

Chromatic aberration

As you can notice in crops, shown below, the tested lens doesn’t have practically any problems with the longitudinal chromatic aberration. We didn’t expect them in such a construction and the Pentax 20-40 mm didn’t disappoint us here.

Pentax HD DA 20-40 mm f/2.8-4.0 ED Limited DC WR - Chromatic and spherical aberration


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The lateral chromatic aberration correction is quite another story – especially the shortest focal length doesn’t look well.

Pentax HD DA 20-40 mm f/2.8-4.0 ED Limited DC WR - Chromatic and spherical aberration


Near the maximum relative aperture and at 20 mm focal length the aberration is close to 0.14% - already a borderline between high and medium level. With the increase of the focal length the aberration decreases: at 30 mm its level can be described as medium and at 40 mm it is already low.

Pentax HD DA 20-40 mm f/2.8-4.0 ED Limited DC WR - Chromatic and spherical aberration

Spherical aberration

We don’t have any serious reservations concerning the spherical aberration correction. The lens doesn’t have any ‘focus shift’ effect and the differences between defocused images of light points you get in front of and behind the focus aren’t pronounced.

Pentax HD DA 20-40 mm f/2.8-4.0 ED Limited DC WR - Chromatic and spherical aberration