I take pictures of products that I sell online but have an issue I just don't know how to correct. The items are placed on a white background inside a small cube "studio" with a light on each side. When I take a picture of a black object, the background is is perfectly white. However when I take a picture of a brass object, the background turns to a shade of gray. It's cast brass so it's not very shiny (if that matters). I use a Panasonic DMC-FZ28 on the Intelligent Auto setting, no flash. I'm not a photographer which is why I heavily rely on the Auto setting however I'd be happy to change any setting that will allow a white background to show properly. And if possible, how to change the setting too.
Thanks for any help!