Comparing bokeh photos using Sony A6000 (ILCE-6000) using 2 lenses:
Sigma 30mm 1:2.8 DN and Sony SELP18105G 18-105 f4
Below are 2 pictures from Sony and Sigma lens with almost exactly the same setting: ISO500, f4, 1/320 sec at about 30mm and within minutes from each other. At the same f stop of f4, both of these lenses are producing very similar images and brightness. Both of these lenses are very sharp.