Also known as the "Kodak neutral test card," a gray card is an 8" X 10" (20 cm by 25.5 cm) card, about 1/8" thick, that is uniformly gray on one side. The gray side reflects precisely 18% of the white light that strikes it (corresponding to the calibration of a reflected-light meter). It is uniformly white on the other side, which reflects 90% of the light.
A reflective card (usually 18% gray), used as a meter target in the determination of exposure.
Card with an 18 percent gray tint (reflectance) used to determine exposure by taking a meter reading from subject light reflected by the card.
a rectangular card that may be purchased at most photo stores
is a gray piece of cardboard used to provide a standard measure of the amount of light reflected by a surface. The gray represents an average tonal value, defined as 18% of the light falling on it. In the Zone System, that is a middle tone, termed Zone V. See also Zone System.
A gray card reflects a known percentage of the light falling on it. Often it has a gray side reflecting 18% and a white side reflecting 90% of the light. Grey cards are used to get accurate exposure readings.
A medium gray card that reflects 17.5 percent of the light falling on it. Used as a standard for medium or average reflectance.
A card that reflect a known percentage of the light falling on it. Often has a gray side reflecting 18 percent and a white side reflecting 90 percent of the light. Used to take accurate exposure meter readings (meters base their exposures on a gray tone of 18 percent reflectance).
Gray cards are used, together with reflective light meters, as a way to produce consistent images in film and photography.
