Hi everyone. So I'm having a bit of a problem. I have started shooting pictures of objects against white backgrounds. For the most part, they turn out okay, I've had three accepted into photostocks. However, I am starting to have a problem. A lot of the times when I take the pictures, the white background ends up turning grey. Here's an example: Is it not powerful enough lighting, or is it something I can adjust on my camera? Thanks for any help.