Since I have seen no dust in my Nikon D600, neither in produced images, it is very interesting suggestion about dust appeared at aperture f/16 and less, which ones no used. I will check it out, but maybe better to photograph, then looking for dust, and strictly to follow the instruction to clean a filter. For me the drug is that at AF-mode C camera often focused on street background rather a moving subject nearest to me. Any suggestion very welcome. David Benyukhis, amatweur photographer.