Comparison of two Sigma AF 12-24 mm zooms on a Canon EOS 10D
No doubt that there are god and bad copies of the Sigma AF 12-24 f:4.5-5.6 EX DG.
Both the tested copies show good resolution at the centre and becomes softer towards the edges. They improve gradually as they are closed down to at least f:11. But while the first copy was hardly usable below f:11 the second copy appears quite usable wide open and very respectable at f:11. In fact the second copy appears to be about as sharp as my former Canon EF 17-35/2.8 USM L at comparable focal lengths and f-stops - at least on a 1.6x cropping camera like the Canon EOS 10D. I will be looking forward to testing and using this lens on a future "full frame" EOS 5D.
Thank you Kamerahuset and Fovitech for providing a good copy at the end.
Some additional tests