Digital Camera Gray Card

Gray cards are used, together with reflective light meters, as a way to produce consistent images in film and photography.

A gray card is an inexpensive and flat object of a neutral gray color that gets light from a flat reflective surface.

In addition to providing a means for measuring exposure, a gray card provides a reference for white balance. White balance, or color balance, refers to the setting that the camera uses to compensate for the color in the scene. Gray cards are useful for white balance since their reflectance is not as intense as that of a plain white object.

Gray cards can be used for in-camera white balance or post-processing white balance. Many digital cameras have a custom white balance feature. A photo of the gray card is taken and used to set white balace for a sequence of photos. For post-processing white balance, a photo of the gray card in the scene is taken, and the image processing software uses the data from the pixels in the gray card area of the photo to set the white balance point for the whole image.

Most digital cameras do a reasonable job of controlling color. For the casual user, a gray card is unnecessary. For the serious photographer or hobbyist, gray cards and color control are an essential and fascinating part of the digital photography process.

Gray cards are made of a variety of materials including plastic, paper, and foam. One of the best gray cards in the market was developed by Digital Image Flow. It's called the Digital Grey Kard and has a white, a gray, and a black card.