# Gray Card

- [[pull]] [[grey card]]
- [[go]] https://en.wikipedia.org/wiki/Gray_card
  - [[quote]] A primary use of gray cards is to provide a [[standard reference object]] for exposure determination in photography. A gray card is an (approximate) realization of a [[Lambertian]] scatterer; its apparent brightness (and exposure determination) therefore depends only on its orientation relative to the light source.