I have tried to blow-brush (one of those brushes that you squeeze and it blows) it away, but there is no way to get rid of it! I have taken the lens off and done it at the body, at the back of the lens... It's still there! How do you get rid of it? It's a Sigma 35-70 AF on a Nikon N50. I only see it thru the camera. If I look at it from the "outside" I can't see it, but I know it will show up at the prints.... Thank you.