Tamron 28-75 mm f/2.8 Di III RXD review - Chromatic and spherical aberration

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Tamron 28-75 mm f/2.8 Di III RXD

26 August 2019

Arkadiusz Olech

5. Chromatic and spherical aberration

Chromatic aberration

The tested lens doesn't have any problems connected to longitudinal chromatic aberration. Photos taken at 50 and 70 mm show that even at the maximum relative aperture and in blurry areas positioned further in the frame the colouring is slight. It certainly won't be bothersome in real life photos.

Tamron 28-75 mm f/2.8 Di III RXD - Chromatic and spherical aberration

Two graphs below show the performance of the Tamron 28-75 mm when it comes to lateral chromatic aberration; the first one presents the edge of the APS-C sensor and the second one - the edge of full frame.

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At 28 mm you don't have any reasons to complain. The results keep a level of 0.06-0.08% so they can be described as low. A bit more reservations we have when it comes to the middle of the focal range because levels of 0.08-0.09% are on the borderline between low and medium values. The most problematic is the 75 mm focal length as the aberration fluctuates with the change of aperture; you can observe the increase of aberration from low by f/2.8 to medium by f/22. Still, it is important that you don't see any high or very high values anywhere even if you deal with a zoom lens which is not only decently fast aperture-wise but also offers you a wide angle of view. Just because of that the Tamron deserves to be praised in this category.

A7R II, RAW, 28 mm, f/11.0	A7R II, RAW, 75 mm, f/16.0

Spherical aberration

First photos from this chapter don't feature any noticeable 'focus shift' effect but spherical aberration is not corrected perfectly well, it's enough you look at photos below. Circles of light reached before the focus are different than those you see after the focal point; what's more, that effect is visible both at 50 mm and 75 mm focal lengths.