18% Grey Card & Neutral Wedge

Why 18% grey?

18% is the reflectance a camera's light meter is calibrated to assume for an "average" scene. A card at that value gives you a known, neutral target: expose so the grey reads mid-tone and your exposure is anchored; sample the grey to set a custom white balance and any colour cast disappears. Because this card is generated at the exact sRGB value for 18% reflectance (sRGB 118), it's more reliable than a photographed or JPEG-compressed card.

Using it to check a grade or LUT

1. Open the card in your editor and apply your LUT or grade
2. The 18% field and every wedge step should stay neutral — equal R, G, and B. Any tint means the grade is introducing a colour cast
3. The wedge shows how your grade handles the full tonal range: watch for crushed shadows at the dark end or blown highlights at the bright end