The index combines Y with the distance of the sample's chromaticity from the neutral white point, scoring a shift toward blue as whiter and a shift toward yellow as less white. Paper practice uses D65 with the 10-degree observer for outdoor daylight (ISO 11475) and illuminant C with the 2-degree observer for indoor light (ISO 11476). Values above 100 are normal for brightened sheets, and office grades often sit between 150 and 170.
Office grade came off at 161 CIE whiteness, five under target, and the tint is creeping green again.
A CIE whiteness number means little without its tint: a high reading with a strong green or red tint will not look right to a buyer.
Also heard as
- CIE W
- CIE whiteness index
Do not mix it up with
- Brightness: Brightness is a single blue-band reflectance, while CIE whiteness uses full colorimetric data and can run far above 100 on brightened sheets.
Related terms
Whiteness
How white a surface looks to the eye, judged across the whole visible spectrum rather than one blue band.
Tint
Companion value to CIE whiteness that tells whether a white leans toward green or toward red.
Illuminant D65
Standard CIE daylight at about 6500 K, with enough ultraviolet to excite optical brighteners strongly.
OBA
Optical brightening agent: a dye that absorbs UV light and re-emits it as blue, making paper look whiter.
Standard observer
CIE model of average human color vision, defined for a 2-degree or a 10-degree field of view.