I haven't seen this discussed extensively and I am curious. We have all seen comparisons of the 12-35 with the 12mm f/2.0, the 20mm f/1.7 etc. But what about the economical choices in this focal range? I.e., the Panasonic 14mm and the two Sigmas (19mm and 30mm). Given that (in Europe, at least) the cost of all three amounts to half the price of the Panasonic, I guess it's a valid question. To avoid missunderstanding, I'm only refferring to IQ and AF performance; the practicality of the Panasonic as well as it's construction quality is beyond discussion.