Why is the use of a Grey Card important?
In an uncontrolled environment (outside or inside under different lighting situations) a Grey Card will help to ensure you get the correct color in your pictures.
You can find the Grey Card App on itunes here.
To use the Gray Card App, simply take a picture of the App in the same lighting your subject is (or was) in. You can either use the resulting picture as the basis for a custom white balance setting, or you can use the Grey Card picture during post processing for a custom white balance.
