Sony FE 40 mm f/2.5 G review - Coma, astigmatism and bokeh

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Sony FE 40 mm f/2.5 G

23 March 2021

Maciej Latałło

7. Coma, astigmatism and bokeh

When it comes to coma correction, I am very pleasantly surprised. I thought in that area we would observe results of compromises but I was wrong. Coma is corrected very well and it's difficult to notice deformations of point-like images of a diode even in the corners of full frame. The only effect you see is a slight blow-up of images compared to the situation in the centre.

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

Astigmatism, understood as an average difference between vertical and horizontal MTF50 function values, amounted to 6.0%. It is a slight value so, once again, you can't find any trace of any negative effects of compromises.

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Defocused circles of light look sensibly well. You can notice the effect of using aspherical elements in the construction so onion-ring bokeh structure is easy to spot. Mechanical vignetting is very strong by f/2.5 but, fortunately, it disappears completely on stopping down the aperture by 2 EV.

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

Center, f/5.0	Corner APS-C, f/5.0	Corner FF, f/5.0