I've been doing photography as a hobby for a while now, and last year I got a cheap fisheye conversion lens (where you can detach the fisheye and be left with a macro lens.) The Macro lens works great, but towards the middle to the outside of the picture on the fisheye, it looks like the color starts to separate from each other. Actually, the entire photo looks like it, but it gets worse towards the edge. Is this because it's just a cheap-o? I do leave on the UV filter and the macro, so would that affect it? I'd really like to just get a real fisheye lens, but unfortunately it's not in the budget right now. I have both a Nikon D50 and D60.