So I have been told by my employer that one of the tools I will need to add to my bag is fisheye lens. Now I have been worried about how much money I am going to have dropped by the end of the summer in terms of equipment. So I see these attachement style fisheye lenses. It seems that you can hook one up to the kit lens or similar. Does anyone have any experience with these screw-on style fish eyes? I know canon makes a 15mm fisheye, But I would love to get away cheaper if this thing performs ok.