Using a gray card is a fast and easy way to set an accurate white balance. A proper white balance eliminates unwanted color casts, so that, for example, skin tones are rendered more naturally and white objects remain a true white in your photos.
ProCamera has a built-in manual white balance feature, as well as an additional method for achieving white balance through what is called ‘gray card’ calibration. The neutral tone of a gray card serves as the reference point for this calibration. It is important that the gray card is positioned in the same light as your actual subject. Once you have calibrated your white balance, which is performed with a long tap on the AWB button, the metered value is locked for continuous shooting until you tap the WB button.
Furthermore, a gray card can be used to adjust the white balance in post-processing software. By having the gray card visible in one of your shots, you will later be able to select a point or pixel on the gray card in your image editing software in order to set a custom white balance.