Thanks for the reply. I'm still a little confused, though. I thought the gray card was to give an adequate exposure setting, not a white balance setting. I am thinking of these as two seperate issues - the amount of light entering the camera (the neutral gray card reflects the magic 18% allowing the camera to correctly adjust for the amount of light thus preventing under/over exposure), and the white balance adjusts for the light temperature. Please help me understand. Thank you.