Its my main portrait lens albeit on a nikon, both outdoors and with studio lights. I have no problems and its nice and sharp. However i have read that some have issues when used with flash and ttl [i think],they misfocus or something, though I am sure someone can be more accurate about the exact problem and I think it would be covered by warranty on a new one and of course it may be the case that sigma has dealt with it on latest models. :shrug: