Video: A range of luminance levels from black to white produced electronically, or shot from a card: A test pattern used for adjusting television cameras and telecines for correct exposure and contrast.
A Test Pattern in the form of a decreasing luminance staircase. Commonly used to check the display’s dynamic grey balance (grey scale tracking).
1. “(video) An optical pattern in discrete steps between light and dark. Note: A gray scale with ten steps is usually included in resolution test charts” [IEEE 100].
2. (production) A card bearing a sequence of neutral (spectrally nonselective) chips arranged in lightness sequence. The chips are of known reflectivity and usually form either a linear or a logarithmic brightness series.
3. The electrical signal which results from, or would result from, the scanning of such an optical pattern.
4. The reproduction of such an optical pattern in a display device.
Grey card
A nonselective (colour neutral) diffuse reflector intended to be lighted by the normal illumination of the original scene, and having a reflectance factor of 18% (compared with a perfect reflector at 100% and prepared magnesium oxide at 98%). The grey card luminance is used as a guide in determining scene exposure so that the image is placed upon the most favourable portion of the transfer function curve.