This is a popular super telephoto lens among sports photographers. By restricting the maximum aperture to f/4.5, a motor-driven 500mm lens weighing only 3kg is realized. High picture quality from ...

[Dan K] had just such a lens from Sigma, but wanted to get it working fully with a camera using the Canon EF lens fitting. Hacking ensued. The lens in question was a Sigma 15-30mm f/3.5-4.5 EX DG ...