scope:

This method specifies a procedure for measuring the color of paper or paperboard with tristimulus filter colorimeters or spectrophotometers incorporating diffuse/0 geometry and CIE (International Commission on Illumination) illuminant C.

NOTE 1: TAPPI T 524 "Color of Paper and Paperboard (45/0, C/2)" describes a similar procedure using directional illumination and normal viewing.

In the method, tristimulus values X (red), Y (green), and Z (blue), appropriate to the CIE-1931 (2°) standard observer, are calculated from reflectance measurements Rx, Ry, and Rz or from R (ʎ) data. Color can then be expressed in various color space systems:   

1. Hunter L, a, b

2. CIE L*, a*, b*

3. L*, C*, h

4. Dominant wavelength, purity, luminosity

5. Color difference, [ΔE, ΔE*, ΔE*94, ΔE (CMC)]

Instruments equipped with microprocessors which give direct information relating to different color scale systems conform to this method only if the means of measurements and calculation conform to the descriptions herein.