Hey everyone. I'm looking to upgrade my current tamron 24-70 2.8 with a newer lens. This lens has become increasingly difficult to use as my photo quality is suffering from a lack of sharpness when used wide open at 2.8 even in the center. I'm looking to find some other options but was looking for some actual user input first. I would consider the Canon 24-70 2.8L mark i lens but am also looking at Sigma however, I've read the same issues are present with that lens as well. Can any of you provide some of your personal input using your lens in concert photography and how it performs? I don't make much $$ from my photography so i'm looking to stay in the $850 range and will consider the Canon mark i lens used. Thanks so much for your input!