Calibrite
CCGB
ColorChecker Gray Balance
The Calibrite ColorChecker Gray Balance is a scientifically engineered 18% gray card to provide an accurate and homogenous surface that is spectrally neutral, thus rendering it suitable as a reference against changes in perceived white tones. This will allow you to adjust your camera's colour sensitivity to match precisely the ambient lighting conditions. It comes in an A4 size of 215.9mm by 279.4mm.