I guess many of us were waiting for this: the possibility to use Sigma's excellent…
Canon DLC Article: Reading and understanding lens MTF charts
Canon Digital Learning Center posted an interesting article about MTF (Modulation Transfer Function) Charts.
Most photography and video enthusiasts have seen “MTF” (Modulation Transfer Function) charts for different lenses, but perhaps have not been entirely clear on exactly what they communicate. We know they’re supposed to give an indication of a lens’ expected optical performance, but beyond that it may be a bit of a mystery. We’ll try to move past the technical terms and explain them here in a real-world way.
[via CDLC]