Gray card / 18% gray card
Grijskaart · Technique
A card that reflects exactly 18% of incident light, used as a reference for correct exposure and white balance.
The camera's light meter is calibrated to 18% gray. If you meter the exposure on a gray card, the technical exposure is always correct regardless of the scene. For white balance, photograph the gray card and use it as a neutral reference point in post-processing.
Tools that help with this: