Good info at digitalartsphotography.com about using a grey card to achieve the proper white balance in photos. It’s important for photographing artworks in order for the color to be represented correctly. I’ve always eye-balled my art photos on the computer monitor, sometimes with horrible results. I’ve heard more than once that the artwork looked even better in person than on the computer screen. I especially liked the tip about saving the custom white balance file for use in similar lighting situations.