either get the inc 16x9 or look at the http://www.bhphotovideo.com/c/product/429702-REG/Century_Precision_Optics_0HD_FESU_HVX_0_55x_Fisheye_Adapter_Lens.html
because with the 16x9 there wont be any vignetting but it doesnt have the most fisheyey look. because its only a .45x with the .55X century your going to have a more horizantol view.
dont get the Opteka .4X ! piece of crap !