ASTM E313-20 pdf free download.Standard Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color Coordinates.
1.1 This practice provides numbers that correlate with visual ratings of yellowness or whiteness of white and near- white or colorless object-color specimens, viewed in daylight by an observer with normal color vision. White textiles, paints, and plastics are a few of the materials that can be described by the indices of yellowness or whiteness calculated by this practice.
1.2 For a complete analysis of object colors, by a specified observer and under a specilled illuminant, use of three parameters is required. For near-white specimens, however, it is often useful to calculate single-number scales of yellowness or whiteness. This practice provides recommended equations for such scales and discusses their derivations and uses, and limits to their applicability.
1.3 The values stated in SI units are to he regarded as standard. No other units of measurement are included in this standard.
5. Significance and Use
5.1 This practice should be used only to compare specimens of the same material and same general appearance. For example, a series of specimens to be compared should have generally similar gloss, texture, and (if not opaque) thickness, and translucency.
5.2 For yellowness measurement, this practice is limited to specimens having dominant wavelength in the range 570 to 580 nm, or Munsell hue approximately 2.5GY to 2.5Y. For whiteness measurement, this practice is limited to specimens having Munsell value greater than 8.3 (CIE Y greater than 65) and Munsell chroma no greater than 0.5 for B hues, 0.8 for Y hues, and 0.3 for all other hues (see 3.3.1).
5.3 The combination of measurement and calculation leading to indices of yellowness or whiteness is a psychophysical process, that is, the procedures specified are designed to provide numbers correlating with visual estimates made under specified typical observing conditions. Because visual observing conditions can vary widely, users should compare calculated indices with visual estimates to ensure applicability. Some standards addressing the visual estimation of color and color difference are Practices D1535, D1729, E1360, and E154l, and Guide El499.
5.4 This practice does not cover the preparation of specimens, a procedure that may affect significantly the quantitles measured. in general. specimens should be prepared and presented for measurement in the manner that is standard for the test being performed. Select enough specimens or specimen areas to provide an average result that is representative of each sample to be tested. See Practice El345.
6. Yellowness Index
6.1 This section contains the calculation of the currently recommended Yellowness Index. The historical background of this Yellowness Index is given in Appendix Xl. Alternative Yellowness Indices are given in Appendix X2.
6.2 calculation of Yellowness Index (YI)—YI can be calculated for either Illuminant C or D65, and either the CIE 1931 standard colorimetric observer (2°). or the CIE 1964 standard colorimetric observer (10°).ASTM E313 pdf download.