Review on Sigma 8mm f/3.5 EX DG Circular Fisheye Lens for Canon SLR Cameras: Wide-Angle Distortion at its Best by Wendy Kennedy

I use this lens to take hemispherical (180 degree) coastal photos for work to determine the level of shade in the tree canopy, this is just what I need and it works great. Note that for a Type-C sensor you need a Sigma 4.5, not an 8mm (full frame) sensor. Both lenses are excellent for this type of work.