Olympus M.Zuiko Digital ED 25 mm f/1.2 PRO
5. Chromatic and spherical aberration
Chromatic aberration
Good aperture fastness is often the source of longitudinal chromatic aberration problems. The Olympus 1.2/25 managed to avoid a slip-up here and the aberration is barely visible – in this category you should praise the lens a lot.
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When it comes to the lateral chromatic aberration the situation is a bit different. Everything is explained by a graph shown below.
Near the maximum relative aperture the aberration reaches 0.14-0.15%, so is within a range we consider too high. Fortunately already from f/2.0 you can talk about medium values and on more significant stopping down they decrease to a borderline between medium and low. Still those results don’t compare favourably with those of the rivals. The maximum result of the Panaleica 1.4/25 exceeded slightly 0.08% and the Voigtlander 0.95/25 fared even better, as its aberration never went higher than 0.05%.
| Olympus E-PL1, RAW, f/1.2 | Olympus E-PL1, RAW, f/5.6 |
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Spherical aberration
Spherical aberration makes itself felt and the appearance of out-of-focus light discs is the proof. It’s a classic case: the circle in front of the focus has fuzzy edges and their brightness falls when you move away from the centre. The circle behind the focus features a lighter rim on the edge for a change.
The aberration described here is not so pronounced when it comes to „focus shift” but you can notice that as well, especially if you compare images got by f/1.2 and by apertures ranging from f/2.0 to 2.8.
| Olympus E-M5 II, f/1.2, in front of | Olympus E-M5 II, f/1.2, behind |
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