That's a cropped image, here's a link to the full size: http://upload.watdo.com/userfiles/willy/IMG_2515_compressed.jpg I tried out all of my lenses and it gives the same "stringy" dust in the same location. When I look through the viewfinder, I can see a speck of something to the bottom right of the center autofocus point. So what is this and what do I have to clean? The mirror, focus screen or sensor? Or is this a scratch of some sort? I have no idea what this is but I'm assuming if I can see it through the viewfinder and it's in my pictures then it's either on the focus screen or mirror, but then again I am probably wrong. Help me out.