Sony FE 50 mm f/1.8 review - Coma, astigmatism and bokeh

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Sony FE 50 mm f/1.8

24 November 2017

Arkadiusz Olech

7. Coma, astigmatism and bokeh

Simple construction of 1.8/50 lenses deal badly with coma and other aberrations influencing the shape of point-like sources of light. The Sony FE 50 mm f/1.8 is not an exception to that rule. At the maximum relative aperture deformations of diode images are visible already in the corners of the APS-C sensor; in the corners of full frame they should be called huge. On stopping down the aperture to f/2.5 you see that aberration decreasing in the corner of the APS-C but in the corner of full frame it remains distinct.

If you want to own a system lens with similar parameters which performs better in this category you have to get interested in the Sonnar 1.8/55 which coma correction was superior.

Center, f/1.8	Corner APS-C, f/1.8	Corner FF, f/1.8

Center, f/2.5	Corner APS-C, f/2.5	Corner FF, f/2.5

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The quite simple optical construction of the lens correct the astigmatism well for a turn. That aberration, understood as an average difference between vertical and horizontal MTF50 function values, amounted to 4.9% so a level we consider to be low. Within the margin of error, it is the same result as that of the Sonnar 1.8/55 FE and the Canon EF 50 mm f/1.8 STM; it also remains noticeably better than the result reached by both Nikkors 1.8/50.

It would be also difficult to complain about out-of-focus areas. Defocused circles of light look nice and the light spread inside seems to be very pleasant. Despite one aspherical element we didn’t notice any traces of onion rings bokeh. A slightly accented rim seems to be the only flaw, and not especially important one. You also should notice a distinct influence of mechanical vignetting.

Center, f/1.8	Corner APS-C, f/1.8	Corner FF, f/1.8

Center, f/2.5	Corner APS-C, f/2.5	Corner FF, f/2.5

Center, f/3.5	Corner APS-C, f/3.5	Corner FF, f/3.5