The DGK R-27 3 Digital Grey Card Set (Set of 3) from DGK Color Tools brings science to the art of digital color control. This Digital Grey Card is the user-friendly, economical and indispensable color correction tool that every photographer needs. The 18% grey side and the 90% reflectance white side help you achieve perfect color in your photos every time. Works with any film or digital camera, for JPEG and RAW files.
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 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.