Normal sharpness in the center starts at f3.5, after f11 he returns to normal only at f8 it was fixed on the carcass, glass is fun and exciting, you can indulge. Has pros: Surprisingly well holds the backlight, there was not even a thought to put a hood on it. Its cons: hence the main disadvantages - unstable autofocus, Chromatitis, but this is at least fixable by the editors.