I am pondering alot over this question. The primes Sigma 20/1,8 EX DG, Nikon AF 20/2,8D or going for the Tokina 12-24 f/4 which is a acceptable pricerange for my economy. I am currently a owner off a 18-70mm which I bought with my Nikon D80. I shoot alot of architectural at the wide angle. As I believe that I will use the lens quite stopped down as I use mostly a large depth of field. I pondering as I want shoot more night shoots which maybe the higher aperture would help from the primes. After spending loads off time at photozone.de reading the same reviews over and again. Will it be worth going prime at wide angle or is zooms better at this length, concerning border to border sharpness? I have seen the mtf charts and so on, but I always have hard time to put this results into how it will look in reality. Especially when photozone not always provide sampleshots. For this lens I would wish good border to border sharpness, more then super duper high sharpness in the middle. Weight is not a issue, heh I am strong swedish viking . Also AF isnt that important as I mostly use manual focus on my 18-70 for external architecture shots. I seen millions of posts on the forums about the wide angle zooms, but I am quite interested in primes. If you got any other prime ideas under 20 mm in that pricerange of the lenses I mentioned earlier, then I am very interested. Cheers, Daniel Ps. Excuse my english for being both not a native speaker and dyslexian Ds.