Quote Originally Posted by dsl712
The 15mm fisheye is a fairly specialized lens. Really not something pulled out of the bag on a daily basis. So I would go with the Sigma. Now if it was a workhorse lens, I would always recommend Canon L series glass.

Much of the difference between some aftermarket lenses and manufacturer lenses has more to do with rugged construction than differences in optics that can be seen with the human eye, operative word being human eye.

Dennis
The Sigma lens also comes with a "four year warranty." I was thinking along those lines that the lens being a fixed, specialized lens that Sigma should work just as good as Canon when it comes to optical results but I needed some confirmation. Thanks for the help! -Justin