Samyang AF 50 mm f/1.4 FE review - Coma, astigmatism and bokeh

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Samyang AF 50 mm f/1.4 FE

7 November 2016

Arkadiusz Olech

7. Coma, astigmatism and bokeh

Coma and other aberrations which deform point-like images are a real curse of the tested Samyang. The aberration is already visible in the corner of the APS-C sensor and you don’t have any problems with noticing it on stopping down the aperture to f/2.0 either.

Center, f/1.4	Corner APS-C, f/1.4	Corner FF, f/1.4

Center, f/2.0	Corner APS-C, f/2.0	Corner FF, f/2.0

Starry sky is even more ruthless for the tested lens. Deformations of images of the stars in the frame corners are clearly visible by f/1.4 and f/2.0; even employing f/2.8 doesn’t mean you can get rid of them. You should emphasize the fact that those images might be a problem not only in astrophotography. Coma and other such aberrations entail decrease of resolution which might be visible in daylight photos as well.

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A7R II, JPEG, f/1.4, lewy górny Corner kadru 1:1

Samyang AF 50 mm f/1.4 FE - Coma, astigmatism and bokeh

A7R II, JPEG, f/2.0, lewy górny Corner kadru 1:1

A7R II, JPEG, f/2.8, lewy górny Corner kadru 1:1

The astigmatism, understood as an average difference between vertical and horizontal MTF50 function values, amounted to 9.9% and it is a result near the middle point of the scale. It means that aberration is not prevailing but it certainly contributes to the overall worsening of the image quality anyway.

Defocused circles of light seem to look sensible but they are hardly perfect. You can notice traces of onion-ring bokeh, most probably connected to three aspherical elements in the construction of the lens. Additionally the mechanical vignetting adds up as it distinctly truncates circles in frame corners near the maximum relative aperture.

Center, f/1.4	Corner APS-C, f/1.4	Corner FF, f/1.4

Center, f/2.0	Corner APS-C, f/2.0	Corner FF, f/2.0

Center, f/2.8	Corner APS-C, f/2.8	Corner FF, f/2.8