Grey card / 18% grey 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% grey. If you meter the exposure on a grey card, the technical exposure is always correct regardless of the scene. For white balance, photograph the grey card and use it as a neutral reference point in post-processing.
Tools that help with this: