Ok Richard I thought you may have included the 17-40mm in your comparison.. Also I   found the sample variations to be something that needs to be taken into consideration, as one was so much better than the other.. But I would certainly agree the the Sigma is wonderful value for money... And for the crop factor nothing to beat it if you get a good one!

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt