I own a Sigma 17-35 f/2.8-4 HSM EX. I am pretty disappointed by its performance mainly because of its severe loss of light and blur at the edge and corner even at f/5.6-8!! I am considering the new 17-40 but most reviews and comments I can find on the web are mainly based on DSLR, which 1.6x factor cannot reflect the quality of the edge portion of a picture. Did anyone use this lens with a film EOS? How's its performance and does it have my aforementioned problems (loss of light and blur at the corner)? Thanks in advance.