Hi all, I foung this link looking up the MTF chart for the 120-300mmF2.8EX lens I have: http://www.sweeting.org/mark/lenses/sigma.php
and unfortuantely it is for Sigma only that I can tell. In the case of similar focal length lenses (ie: Canon 70-200 and Sigma 70-200) this wil be rather interesting. Enjoy!

take a look: 
