For a more real-world test (based on shooting photos with this lens) you can look at Steve Huff's review of this lens, where he concludes...
"Great sharpness, contrast and color. Truly pro quality and great on the OM-D E-M5."
"Panasonic has another winner on their hands, though a pricey one and this lens can stand toe to toe with the Nikon and Canon 24-70 equivalents while being MUCH smaller."
Panasonic 12-35 f/2.8 Zoom Lens Review for Micro 4/3
Plenty of reports claiming it's not so impressive and not as good as the Zuiko 12-40 at the corners and edges. I'm not buying a 3rd copy......
