Olympus M.Zuiko Digital 300 mm f/4.0 ED IS PRO review - Coma, astigmatism and bokeh

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Olympus M.Zuiko Digital 300 mm f/4.0 ED IS PRO

30 June 2016

Arkadiusz Olech

7. Coma, astigmatism and bokeh

One glance at thumbnails below and you know that also in this case the optics specialists from Olympus did exceedingly well. Even at the maximum relative aperture and in the very corner of the frame it is difficult to notice any influence of the coma on the shape of the diode.

E-M10, 300 mm, f/4.0, center	E-M10, 300 mm, f/4.0, corner

E-M10, 300 mm, f/5.6, center	E-M10, 300 mm, f/5.6, corner

The situation changes slightly after attaching the tele-converter. It would be difficult to talk about a distinct or high coma level because the lens still corrects that aberration in a proper way. However its slight influence can already be noticed because the image of the diode in the frame corner becomes a bit elongated.

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E-M10, 420 mm (TC), f/5.6, center	E-M10, 420 mm (TC), f/5.6, corner

E-M10, 420 mm (TC), f/8.0, center	E-M10, 420 mm (TC), f/8.0, corner

When it comes to the astigmatism understood as an average difference between vertical and horizontal MTF50 values there are no problems whatsoever. The lens itself generates a very low astigmatism level, that of 4.1%, and after attaching the tele-converter that level increases to 5.5%. Both values should be deemed low.

The out-of-focus areas generated by the Olympus 4/300 are quite pleasing to the eye and defocused light circles we managed to get prove that much. The circles are beyond reproach; they don’t even feature traces of mechanical vignetting as in the very corner of the frame the images keep a more or less circular shape. The brightness of the rim, increasing on stopping down, is the only thing you can notice here and it concerns both the performance of the lens on its own and with the tele-converter attached.

E-M10, 300 mm, f/4.0, center	E-M10, 300 mm, f/4.0, corner

E-M10, 300 mm, f/5.6, center	E-M10, 300 mm, f/5.6, corner

E-M10, 300 mm, f/8.0, center	E-M10, 300 mm, f/8.0, corner

E-M10, 420 mm (TC), f/5.6, center	E-M10, 420 mm (TC), f/5.6, corner

E-M10, 420 mm (TC), f/8.0, center	E-M10, 420 mm (TC), f/8.0, corner

E-M10, 420 mm (TC), f/11.0, center	E-M10, 420 mm (TC), f/11.0, corner