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2-3EV OIS plus perhaps 1.5-2EV extra in Dual IS
6.1% (1.6% after jpg correction) barrel distortion at 12mm and minimal thereafter
2.08 EV (0.7EV corrected in jpg) vignetting at 12mm f/2.8, minimal at other focal lengths (0.7EV or less wide open uncorrected)
excellent sharp centres but towards edges just good sharpness at 12mm , better at other focal lengths
some field curvature so use at least 1 stop down for infinity subjects to maintain focus edge to edge
low CA levels
bokeh - some onion ring effects, and in scenes with harsh contrasts, “The rendition of blur in the critical focus transition zone is not optimal. The blur is not symmetrical resulting in fairly hard edges. The more important background is smoother than the image foreground.”