It has been written a lot of good about this glass. Therefore I do not use repetition. I'm in love with photography for over 50 years and an uncompromising quality fanatic. I am not interested to the number of lines per mm, but the image (and its sharpness and color reproduction.). That's why I was with recent wide-angle lenses (I can only on Canon and other major vendors refer) always dissatisfied with the imaging performance outside the center. My Canon 17-40 just generated only pixels mud in the extreme corners. Not so with the new Canon. Very good sharpness and perfect contrast to the corners dimmed, even without visible difference. I never had -apart from 100 L-macro a sharper lens on the EOS 5D Mark II with a set. I'm thrilled! Incidentally, there is a good Traumflieger video for this objective compared with other Weitwinkel.Gut, it's not cheap, but the joy that comes when shooting with this lens, it is worth.