Kerry . . . I'm late to this thread, but I just found
this comparison between the Tamron and the Canon. There are lots of photos using both lenses for comparison and prices from Adorama too. Interesting thoughts here that might help your decision. Let us know what you decide and show us the fantastic photos that you take with which ever lens you choose.
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Mollie
My DD Gallery
DD Photo-a-Day Flickr Group
Software: Photoshop Elements 8.0
My Gear: Canon PowerShot G10, Canon D50
, Tameron 28-300 lens and Canon 50mm - 1.4 lens
Computer: iMac