used Sigma/Canon question

[thegarageblog]

I have become a semi pro motorsport photographer, but I really am just a car guy/automotive writer geek, not a camera geek. My 30D is a workhorse tool, but the lens bug has bit. I took a chance and bought a pair of Sigma lenses off ebay. They were sold really cheap and the seller did say that some functions did not work on his new Tsi. I figured that I would take a gamble and see if they worked with an older model like my 30D.

They don't, or at least not consistently. Sometimes I get an error 99, while other times they seem to work fine and will shoot a pic.

Any suggestions?