I have my Rebel XT, but notice that when I photograph dark or black objects, they look like they have different colors in them or some grainyness or noise. This can only be seen when the picture is at 100% and at it's highest resolution setting. When it's about 4x6 size print, it can't be seen. Is there anything wrong with the camera? I know the lens is the kit lens, but is this supposed to happen with the blacks in digital photography?