New Sigma 17-70 2.8 lens

Just from the name and designation you will not be able to tell the difference. However the older lens has a golden band at the coupling end which is absent in the new model. The latter also is supposed to have a "C" at the end of the model notation - tough to find at first glance. Until the lens is tested by an independent lab its difficult to say if there is significant improvement in its performance - however the news is that Sigma have addressed some of the shortcomings (such as softening at the plus 50mm end) present in the old model - if they have then they have a winner !