We were talking about white balance targets and I've had these Whibal cards for a long time. I've never found that they give me exactly what I want, but when you have an image with not white or grey point to click on for color adjustment in a raw converter, they do give a good starting point. You can learn more about how the cards are used here: http://www.whibalhost.com/_Tutorials/WhiBal/01/index.html