The bispectral or two-monochromator method is the definitive method for the determination of the general (illuminant-independent) radiation-transfer properties of fluorescent specimens (2). The Donaldson radiance factor is an instrument- and illuminant-independent photometric property of the specimen, and can be used to calculate its color for any desired illuminant and observer. The advantage of this method is that it provides a comprehensive characterization of the specimen's radiation-transfer properties, without the inaccuracies associated with source simulation and various methods of approximation.

This practice provides a procedure for selecting the operating parameters of bispectrometers used for providing data of the desired precision. It also provides for instrument calibration by means of material standards, and for selection of suitable specimens for obtaining precision in the measurements.

1.1 This practice addresses the instrumental measurement requirements, calibration procedures, and material standards needed for obtaining precise bispectral photometric data for computing the colors of fluorescent specimens.

1.2 This practice lists the parameters that must be specified when bispectral photometric measurements are required in specific methods, practices, or specifications.

1.3 This practice applies specifically to bispectrometers, which produce photometrically quantitative bispectral data as output, useful for the characterization of appearance, as opposed to spectrofluorimeters, which produce instrument-dependent bispectral photometric data as output, useful for the purpose of chemical analysis.

1.4 The scope of this practice is limited to the discussion of object-color measurement under reflection geometries; it does not include provisions for the analogous characterization of specimens under transmission geometries.

This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.