By using this set of three cards - Black, White and Neutral Gray simply take a picture of the card in the same lighting your subject is (or was) in. Use auto white balance and P (Program) mode for the picture. You can either use the resulting picture as the basis for a custom white balance setting, or you can use the White Balance Card Set picture during post processing for a custom white balance.

The glossy surface of the White Balance Card Set will instantly reveal any reflections that may lead to incorrect white balance. If reflections are seen on the Card surface during a white balance operation, reposition the Card so that reflections are eliminated.