Excerpt: There are two types of fisheye: circular and diagonal. The Rokinon 8mm f/3.5 Aspherical Fisheye Lens is of the diagonal type, delivering a rectangular image with cropped-sensor lenses. The lens I worked with is designed for the Nikon DX (APS-C/cropped) sensor. The APS-C version provides a 180-degree field of view. Other versions are available for other “cropped-sensor” interchangeable-lens cameras, including Micro Four Thirds.