Not familiar with the F50 , which mode are you shooting in ?
You mentioned a light box , but what about the lights ? Key is to not only getting light , but getting the right light ( temperature wise ) , if you shoot in RAW you can adjust your white balance after the shot ( post production ) , you can do adjust it while shooting in jpeg as well after the shot , just not as well.
with a light box , you should not be using the flash on camera .
An image of what you have so far would go a long way towards suggesting what to change / adjust.