Olympus M.Zuiko Digital ED 8-25 mm f/4 PRO review - Coma, astigmatism and bokeh

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Olympus M.Zuiko Digital ED 8-25 mm f/4 PRO

26 October 2021

Maciej Latałło

7. Coma, astigmatism and bokeh

Photos below prove that the Olympus M.Zuiko Digital ED 8-25 mm f/4 PRO deals with coma pretty well. Images of a diode, even these in frame corners and at the maximum relative aperture, are just slightly deformed so the lens should be praised for its performance in this category.

E-M5 II, 8 mm, f/4.0, center	E-M5 II, 8 mm, f/4.0, Corner

E-M5 II, 16 mm, f/4.0, center	E-M5 II, 16 mm, f/4.0, Corner

E-M5 II, 25 mm, f/4.0, center	E-M5 II, 25 mm, f/4.0, Corner

Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 8.9% -it's a value situated on the borderline between low and medium level. You can also mention the fact that this aberration is very low at the maximum focal length (just 3.3%), and distincly higher from 8 to 16 mm (about 11-12%).

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Blurry areas produced by the Olympus 8-25 mm don't look especially nice but with such wide angles of view and such a depth of field it would be difficult to get a better effect. The area of the circles is marked with a a brighter rim and aslo lot of heterogeneities caused most likely by aspherical elements, present inside the lens. Fortunately the influence of mechanical vignetting is negligible.

E-M5 II, 25 mm, f/4.0, center	E-M5 II, 25 mm, f/4.0, Corner

E-M5 II, 25 mm, f/5.6, center	E-M5 II, 25 mm, f/5.6, Corner

E-M5 II, 25 mm, f/8.0, center	E-M5 II, 25 mm, f/8.0, Corner