>>2663907hmmm. 6400 is the top of the usable range. then there's hi1/hi2 (25600 max i think). as I said, i've shot in clubs many times with the ISO between 2500 and 3200 and never had this issue. I just did some ISO tests with similar settings and it didnt happen again, yet most of the shots from that night had traces of it. It was shot in RAW. pic related is the entire lightroom history + how it appears in develop mode, until you zoom in or export, in which case you get the above. i havent noticed it since, but i havent shot in low light/at a gig since. if it happens again i'll seek additional help. might be time to upgrade anyway