JJC GC-3 3-in-1 Digital Grey Card is a multi-function system, which has many function for both conventional and digital cameras. With the developing of digital photography, color balance become the responsibility of every photographer. Most digital cameras have an auto white balance (AWB) feature built-in. AWB uses image data from bright areas in the photographed scene to set the color temperature. However, in a scene with no bright areas, or if the light has a very strong color cast, even expensive digital SLR cameras will perform poorly. Now, you will need the grey card or white card to set a true white balance, resulting in a more accurate recording of all the colors. In addition, you will be able to set proper exposure using the 18% neural grey card as well. The black card can be used to block away some stray light to get an normal exposure.