Olympus M.Zuiko Digital ED 25 mm f/1.2 PRO review - Coma, astigmatism and bokeh

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Olympus M.Zuiko Digital ED 25 mm f/1.2 PRO

10 January 2017

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Szymon Starczewski

7. Coma, astigmatism and bokeh

The Olympus 1.2/25 doesn’t correct the coma in a perfect way - you can notice slight deformation of the diode in the frame corner both at the maximum relative aperture and on stopping down the lens by 1 EV. Still it would be difficult to talk about serious problems because the level of that aberration is medium at most. Anyway the tested lens fares noticeably better than the Voigtlander 0.95/25 and the Pana-Leica 1.4/25.

E-M5 II, 25 mm, f/1.2, center	E-M5 II, 25 mm, f/1.2, corner

E-M5 II, 25 mm, f/1.8, center	E-M5 II, 25 mm, f/1.8, corner

The astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 17.6%. It is a high value. What’s more that aberration is noticeable even at apertures ranging from f/2.8 to 4.0, one of the reasons why the tested lens didn’t manage to get to a level of 80 lpmm with its MTFs.

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Light discs we got in out-of-focus areas look nice. The light spreads evenly, without any distinct local extremes. You can notice two things, though. Firstly, on stopping down the aperture a lighter rim appears. Secondly, at the maximum relative aperture the disc has soft edges and the brightness loss in its upper area is a bit more pronounced than downwards. It might be connected to mechanical vignetting.

E-M5 II, 25 mm, f/1.2, center	E-M5 II, 25 mm, f/1.2, corner

E-M5 II, 25 mm, f/1.8, center	E-M5 II, 25 mm, f/1.8, corner

E-M5 II, 25 mm, f/2.5, center	E-M5 II, 25 mm, f/2.5, corner