This gray card is to provide a standard reference object for exposure determination in photography. Its apparent brightness (and exposure determination) therefore does not depend on its orientation relative to the light source. By placing a gray card in the scene to be photographed, oriented at a defined angle relative to the direction of the incident light, and taking a reading from it with a reflected light meter, the photographer can be assured of consistent exposures across their photographs. In addition to providing a means for measuring exposure, a gray card provides a convenient reference for white balance, or color balance, allowing the camera to compensate for the illuminant color in a scene. 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 balance 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. Many serious photographers or hobbyists consider gray cards an essential part of the digital photography process. Features: 18% grey card reflector. Works with your light meter or digital camera. White color on back side. Comes with a zippered bag. Specifications: Model: R-21 Material: PU, could be cleaning with water Color: Grey & White Card Size: Approx. 60 * 60cm / 24 * 24in Package Size: 24 * 23 * 3.5cm / 9.4 * 9.1 * 1.4in Package Weight: 370g / 13oz Package List: 1 * 18% Gray White Balance Focus Card 1 * Carrying Bag