Umm, if I may note something... If your camera is anything like mine, these had to be shot at different focal lengths, right? I cannot get 1.8 (no, it's not a mistake, 1.8) except at the widest setting. The more you go towards tele lengths, the smaller is the aperture. (Generally speaking!) Wide angle has nicer side sharpness, while tele has nicer depth sharpness. So the blurring depends on that. Which would be kinda confirmed by your pics, no? Or I'm wrong?

-- erlik