Lens review

Leica D Summilux 25 mm f/1.4

5. Chromatic aberration

The first reason of the Leica’s lower frame edge resolution is certainly the horizontal chromatic aberration, which blurs the vertical borders. If, in the case of the Olympus 3.5/35 and 2.0/50 lenses it was slight, in the case of the Leica it is definitely bigger. Looking at the chart below, we see that, at the maximum relative aperture the level of this aberration can be described as average, even bordering with low. It gets bigger, though, when we run through the aperture scale, reaching the borderline between average and high values.

Exactly this aberration level increase on stopping down is partially the reason of weaker frame edge performance. Stopping down reduces other aberrations so the resolution should increase. Here, it doesn’t increase as fast as it should because it is limited by the increasing chromatic aberration.

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If you want to be objective, you must notice that Leica still fares pretty well, when compared to its competitors. The Canon 1.4/35 on the 20D sensor showed aberration on the level from 0.12 to 0.14 % so definitely bigger.