Don't be fooled by wherever you read that. The angle of view is usually quoted for an 'APS-C' image circle whose diameter is the diagonal of (
originally) 25.1mm x
Sorry about the loss Ted,I hope you will get a good one soon:-)
16.7mm. However, should you happen to own a Canon 1100D, your sensor size is smaller than that (22.2mm x 14.7mm). Which means that neither the Sigma nor the Tokina would get that wide on your camera.
By coincidence, I'm bidding on a Sigma 10-20mm today . . .
[edit] . . . and just lost to a higher bidder