Quote Originally Posted by clemmb
The Tamron is a great lens for the price but the image quality from the canon is noticeably better.

I kindly disagree. The 24-105 has better build, focus, IS, and other advantages, but image quality is not one of them. They may be close enough to equal under some circumstances, but many times the Tamron will eat it for lunch. The Canon 17-55 is a different story.