I've never had great success with color balance cards. Right now I am using a Michael Tapes pocket gray card that is supposed to be within 0.5 on the a & b channels for the gray patch (comes with black and white patches too). I used it in my most recent shoot where I had only one light. After I balance off the card in Adobe Camera Raw, my images don't look good--the color temperature is off in the image-the green/magenta amounts as well as the Kelvin temp. I am working off a color calibrated monitor. I usually end up balancing by eye and using neutral points in the image for numerical reference. It seems like the gray card's only use for me is so I can look professional in front of my clients. Does anyone have any ideas or have had similar problems?