astounding resolution wide open at 12mm and good resolution at 60-100mm (although these focal lengths are sharper at f/5.6) and performance across the frame is very good - perhaps the best results for any 8x zoom lens ever made
overall resolution even better then the Panasonic Lumix G 12–60 mm f/3.5–5.6 ASPH. POWER O.I.S, and much better than the Olympus mZD 12-50mm lens
doesn’t have any problems with the longitudinal chromatic aberration no matter what focal length
minimal lateral CA, but medium to high at 25mm wide open
RAW uncorrected distortion is relatively high but corrected in jpegs to minimal:
minimal astigmatism and coma
vignetting maximal on older sensors at 1.54 EV (corrected in camera to 0.88 EV) for 12mm f/4, less on newer sensors