The Page of Omnidirectional Vision. Hosted by the GRASP Laboratory, maintained by Kostas Daniilidis, part of the IEEE Robotics and Automation Society, TC on Computer and Robot Vision activities.
Page of Catadioptric Sensor Design. Course on Omnidirectional Vision at ICCV 2003. In Memoriam. Comparison_Nikkor Vs Sigma Short_Eng. Update 17 June, 2006 Last rev. 15 December 2006 Why this comparison?
From my point of view, these two lenses are currently the most popular short-focal-fisheye lenses that are used by the Panorama Photographers. On many forums, when asking for what is a the best gear to shot photographs and make panorama the easiest way , the newbies are answered invariably: Mashup of SmugSmug and Googlemap.