Hey Im fairly new to photography but recently bought a second hand Canon 40D from a shop in Manchester a couple of days ago. But all of my images, no matter what lens are on the camera have these three marks on them. this is a picture of a completely clear sky: http://img36.imageshack.us/img36/9607/img074001.jpg But as you can see from the image there are multiple marks. 2 of which are very bad. Is there any way that i can fix this from home without taking it back? And will they even take it back? It came with a 30 day warranty. Any help much appreciated!