Calculation of Yellowness Index and Whiteness Index Using Instrumental Color Coordinates

Meaning and use
5.1 This practice should only be used to compare samples of the same material and the same general appearance. For example, a range of specimens to be compared should have roughly similar lustre, texture and (if not opaque) thickness and semi-transparency.

5.2 For yellowness measurements, this practice is limited to samples whose main wavelength is in the range 570 to 580nm or whose Munsell hue is approximately 2.5GY to 2.5Y. For whiteness measurements, this practice is limited to samples with Munsell values greater than 8.3 (CIEY greater than 65) and Munsell chromaticity no greater than 0.5 (B tone) and Munsell chromaticity no greater than 0.5 (Y tone 0.8) and all other tones of 0.3 (see 3.3.1).

5.3 The combination of measurement and calculation that results in a yellow or white index is a psychophysical process, that is, the specified procedure is designed to provide numbers relevant to visual estimates made under specific typical observation conditions. Since visual observation conditions vary widely, users should compare the calculated index with visual estimates to ensure applicability. Some standards that address color and chromatic aberration vision estimation are Practices D1535, D1729, E1360, and E1541, as well as guidelines E1499.

5.4 This practice does not include specimen preparation, a procedure that can have a significant impact on the amount measured. Typically, samples should be prepared and presented for measurement in a standard manner for the tests performed. Select enough samples or sample areas to provide average results representative of each sample under test. See Practice E1345.

Calculation of Yellowness Index and Whiteness Index Using Instrumental Color Coordinates

1.1 This practice provides numbers associated with visual ratings of yellow or white for color specimens of white and near-white or colorless objects, viewed in daylight by observers with normal color vision. White textiles, paints and plastics are some of the materials that can be described by the yellow or whiteness index calculated in this way.

1.2 In order to perform a complete analysis of object color by a specified observer and a specified light source, three parameters need to be used. However, for near-white specimens, it is often useful to calculate a singular scale of yellowness or whiteness. This practice provides recommended equations for this scale and discusses their derivation and use, as well as the limits of their applicability (see also References (1) 2).

1.3 Values expressed in SI units shall be treated as standard values. No other units of measurement are included in this standard.

1.4 This standard is not intended to address all, if any, safety concerns associated with its use. It is the responsibility of users of this standard to establish appropriate safety, health and environmental practices and to determine the applicability of regulatory restrictions prior to use.

1.5 This international standard is based on the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the WTO Committee on Technical Barriers to Trade.

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