8 out of 10 points and recommendedExcellent center sharpness. Good corner sharpness when stopped down. Good autofocus, fast and accurateSoft in corners at 12mm until f/11-16. Some CA seen.
Soft in corners at 12mm until f/11-f/16. A little more CA than I had hoped with all that FLD glass. More barrel distortion at 12mm (but easy to correct) than I saw in tests of original version lens (I don't have it). Not as good on full frame as the Sigma 8-16mm is on APS-C.reviewed August 31st, 2011 (purchased for $949)
Excellent landscape lens. Good corner sharpness when stopped down. Better than my beloved 17-40L Canon. (They have similar MTF charts). Good autofocus, fast and accurate.
I tested the new version vs Canon 17-24mm L at 17mm and 24mm focal lengths on Canon 5d (FF). The 12-24 has much better corner sharpness than the Canon at 17mm and equal or better corner sharpness at 24mm at all apertures. (Both are good at 24). At 12mm, the extreme corners (last 2-3mm) are very soft wide open and soft until f/11 (pixel peeping at 100%). No issues with sharpness when used on APS-H or Aps-C crop cameras. Not as sharp in corners as 14mm F2.8 Samyang/Rokinon.