Sony DT 18-70 mm f/3.5-5.6 review - Chromatic aberration

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Sony DT 18-70 mm f/3.5-5.6

22 October 2010

Arkadiusz Olech

5. Chromatic aberration

The mysterious „something” which appeared near the end of the last chapter is of course the chromatic aberration. If we have to tell the truth, in the 18-30 mm range its level is monstrous. I remember how much we complained about the Sigma’s 18-50 f/2.8 performance in this category, which was simply record-breaking, reaching the level of 0.18%. The Sigma is no match for the tested Sony, though…Bad resolution results at the edge of the frame are clearly explained. There is no good resolution in a place where you can’t focus the whole visible spectrum in a sensibly small field of vision. At the wide angle the Sony can’t do that.

Sony DT 18-70 mm f/3.5-5.6 - Chromatic aberration

The crop below shows the situation at the edge of our test chart.

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The graph of the real profile on the white and black border, when separated into the basic colours, is also an interesting thing. It is shown, for a change, in the next picture, produced by the Imatest programme.

All things considered, the lens’s metamorphosis in the 50-70 mm range is even more stunning. The aberration level there is not only acceptable but in some cases it can be even called low. Intriguing indeed!

Being a bit mean you must admit that Sony is a very honest company. The description of the tested lens, published on the website of the producer, features such a fragment: "ED (Extra-low Dispersion) Glass: To reduce chromatic aberration at telephoto extension, correcting certain wavelengths of light for sharp, clear images with well defined colors." As you see, it is clearly stated that the producer promises the chromatic aberration reduction only in the 50-70 mm range. They kept their promise…