Calumet Photo offers the Sigma 4.5mm f/2.8 EX DC Circular Fisheye Lens for Canon
, model no. 486-101, for $591.99
with free shipping
. That's the lowest total price we could find by $138. This 180 degree circular fisheye lens features a minimum focusing distance of 13.5cm and a maximum magnification of 1:6.