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Sigma 8-16mm f/4.5-5.6 EX DC (vs Sigma 12-24 on FF)
For years, there has not be any equivalent of the Sigma 12-24 for APS-C users. I have really appreciated the 12-24 on FF, and I wished to see something similar for my Canon 7D. In early 2010, Sigma has announced such lens: the 8-16mm, a lens created exclusively for APS-C cameras. It gives exactly the same angle of view of the 12-24 on FF (if you have a Nikon APS-C camera, 1.5x crop factor), and a very similar angle of view on Canon APS-C cameras, that have a 1.6x crop factor. I have tested this lens on my 7D and I have compared it with the 12-24 on 1Ds3!
As usual, I recommend to give a look to the page Testing and reviewing a lens: it will help you to understand better this review and my testing methodology!